They do not qualify as a witness

Imam Ja'far as-Sadiq (a.s.) is reported to have said, 
"The false witness must be lashed, and the number of lashes is determined by the Imam (or the Islamic judge) and he should be paraded (in the city) till people know him (and may not rely on him in the future)."

The Imam (a.s.) recited the following verse of the Quran: 
"...and do not admit any evidence from them ever; and these it is that are the transgressors, except those who repent after this and act aright, for surely Allah is Forgiving, Merciful."
(Surah Nur 24:4-5)

(It means that after he repents and reforms, his evidence again becomes valid)

The narrator says that he asked Imam (a.s.), "How do we know that he has repented?"

Imam (a.s.) replied, 
"At the site where he is lashed, he must confess in public that he had given a false testimony. And he must seek the forgiveness of Allah. In this way it could be known that he has repented." 
(Wasaelush Shia)

Compensation for the loss

If, due to a false testimony a Muslim has had to suffer some monetary loss or loss to one's life or property, the witness has to make good the loss. A narrator by the name of Jamil inquired from Imam Ja'far as-Sadiq (a.s.) regarding the one who has testified falsely. Imam (a.s.) told him: 
"If the disputed property is still intact it must be restored to the rightful owner. If it is not then the false witness is responsible to the extent of it's loss." (Masaalik)

This means that if it is not possible to return the property, the false witness will have to reimburse it by providing a thing similar to that property or pay a price for it. Detailed laws are discussed in the books of Islamic Jurisprudence.

Repentance for the sin

The method of repenting for the sin of giving false testimony has already been explained. The first important requirement is that the sinner must feel a deep remorse for the act committed by him. He must also seek the forgiveness of Allah for disobeying His command; and compensate the Musilm who suffered the loss. As Allah Himself says, 
"…except those who repent after this and act aright, for surely Allah is Forgiving, Merciful." 
(Surah Nur 24:4-5) 

To refrain from testifying in an Islamic Court is clearly classified among the 'Greater sins' according to the authentic tradition narrated by Hazrat Abdul Azeem. There are some situations when it is Wajib to prove right what is right and to prove wrong that is wrong. In the narration mentioned in the previous discussion, Imam Muhammad al-Baqir (a.s.) states that to conceal evidence is a 'Greater sin'. He presents the following verse as the proof: 
"...and do not conceal testimony, and whoever conceals it, his heart is surely sinful; and Allah knows what you do." 
(Surah Baqarah 2:283)

This verse mentions the sinful heart (his heart is surely sinful). There are two noteworthy points in this. One: That the concealing of testimony is a sin of the heart. The heart alone commits it, and other organs are not apparently involved in it. The person hides the reality in his heart and does not speak out. Secondly, just as the heart is superior to all the organs of the body the sin associated with the heart is also greater than the sin performed with other organs. It is just like the obedience of Allah through ones heart is much superior than obeying Him in actions. It is this same heart that involves one in a great sin like polytheism. These sins of the heart are definitely more than sins associated with other organs. One of the sins of heart according to the ayat of Quran is concealing evidence. In order to emphasise, Allah says in the later portion of this ayat, "...Allah knows what you do", so that the sinner may realise that even though people may not be aware of Allah is awareof his sin and He will certainly punish him for it.

Allah the Almighty also says, 
"...and the witnesses should not refuse when they are summoned." 
(Surah Baqarah 2:282)

Similarly in another verse, Allah says, 
"And who is more unjust than he who conceals a testimony that he has from Allah?" 
(Surah Baqarah 2:140)

Such a person is like the Jews and the Christians, who had seen the characteristics of the Holy Prophet (s.a.w.s.) in the Torah and Injeel but deliberately concealed them.

Testify for the truth even if it harms you

In Surah Nisa, the Almighty Allah says, 
"O you who believe! Be maintainers of justice, bearers of witness for Allah's sake, though it may be against your own selves or (your) parents or near relations; if he be rich or poor, Allah is nearer to them both in compassion; therefore do not follow (your) low desires, lest you deviate; and if you swerve or turn aside, then surely Allah is aware of what you do." 
(Surah Nisa 4:135)

Thus one must not conceal testimony due to the fear of the rich or mercy for the poor. One must not feel undue compassion for the accused who is poor. One should neither pay heed to ones own interest nor care for any other person while giving testimony. The Divine command should always be respected in entirety.

Justice for the enemy

The following verse of Surah Maidah states:
"O you who believe! Be upright for Allah, bearers of witness with justice, and let not hatred of a people invite you not to act equitably; act equitably, that is nearer to piety, and be careful of (your duty to) Allah; surely Allah is aware of what you do." 
(Surah Maidah 5:8)

According to this ayat testimony should be given only to seek the pleasure of Allah. No feeling of enmity should be allowed to come in the way of stating the truth. Allah (a.j.) says in another verse:
"...and give upright testimony for Allah." 
(Surah Talaq 65:2)

Those who conceal evidence

Imam Muhammad al-Baqir (a.s.) remarks, 
"On the Day of Qiyamat, Allah shall cut off the flesh of one who conceals evidence; then order him to eat it before all the creatures." 
(Wasaelush Shia)

Imam Muhammad al-Baqir (a.s.) also says that those who conceal evidence are described in the Quran as those whose hearts have sinned. 'Hearts have sinned' actually implied that 'hearts have disbelieved'," according to Imam (a.s.)

Another tradition recorded from Imam (a.s.) is thus: 
"One who goes back upon his testimony or conceals it wholly, Allah shall cut off his flesh and force him to eat it before everyone. And when he will enter Hell he would be chewing at his own tongue." 
(Wasaelush Shia)

Hazrat Imam Musa al-Kazim (a.s.) says, 
"When you are asked to give evidence, give it. For Allah (a.j.) says: 
"Surely Allah commands you to make over trusts to their owners..." 
(Surah Nisa 4:58)

Evidence is itself a trust. Allah (a.j.) also says, 
"And who is more unjust than he who conceals a testimony that he has from Allah?" 
(Surah Baqarah 2:140) (Wasaelush Shia)

The following tradition of Amirul Momineen Ali (a.s.) is recorded in Tafseer Ali Ibn Ibrahim Qummi: 
"One who possesses some evidence, has to make it known. And when he is asked for it, he must give it. He should not fear anyone's criticism. He must fulfill his obligation of Amr bil Maroof (enjoining good) and Nahi Anil Munkar (forbidding evil)."

Is it wajib to testify?

Is it wajib to become a witness if one is requested to do so by a believer brother, in order he may achieve some benefit from the case he is pursuing in an Islamic Court? According to most of the Mujtahids it is wajib. Allah the Almighty Himself says:
".,.and call in to witness from among your men two witnesses; but if there are not two men, then one man and two women from among those whom you choose to be witnesses, so that if one of the two errs, the second of the two may remind the other; and the witnesses should not refuse when they are summoned." 
(Surah Baqarah 2:282)

Hisham says that Imam Ja'far as-Sadiq (a.s.) said, 
"And the witnesses should not refuse when they are summoned."
(Surah Baqarah 2:282)

And in the succeeding ayat, 
"...and do not conceal testimony", meaning concealing testimony from a Shariat judge."

Numerous traditions state that to be a witness is wajib (obligatory). For example, Muhammad Bin Fuzail asked Imam Musa al-Kazim (a.s.) the meaning of the above ayat (Surah Baqarah 2:282)

"And the witnesses should not refuse when they are summoned."

Imam (a.s.) replied, 
"When someone calls you to give evidence in a matter of some debts or some right, then you do not have the choice to ignore it." 
(Wasaelush Shia)

Of course the Quranic command in the verse 282 of Surah Baqarah asking the witness to testify before the Shariat judge implies that the person had in the first instance been a witness to the transaction etc.

The person who has witnessed the transaction etc. has to exercise extreme care and caution in this regard. He must memorise all the details or put them in writing, if necessary, so that there is no scope for doubt or misunderstanding in future. If this person is called upon to be a witness, it is wajib on him to comply, even if he has to roam some distance.

People whose supplications are not accepted

Hazrat Imam Ja'far as-Sadiq (a.s.) says: 
"Dua of four types of people is not answered: 
1. A Person who sits idle at home and prays to Allah to provide him with sustenance is told, 'Have We not ordered you to make effort for obtaining your sustenance?'

2. The person who prays for some misfortune for his wife. He is told, 'Have We not given you the choice of giving her divorce if you do not want such a wife?'

3. One who had squandered the money and spent it in evil ways. Now if he prays for sustenance, he is told, 'Did We not order you to spend in moderation?'

4. One who gives a loan to someone but does not make anyone witness it. Hence if the borrower refuses and the creditor prays, he is informed, 'Had We not ordered you to have witnesses?'"
(Iddatud Dai)

Testifying is wajib and concealing evidence, haraam

There may be occasion when a person has not directly witnessed a transaction but has some information for having heard or seen something related to the issue. If the information he has can save a Muslim from harm or enable him to secure his right, it is wajib on this person to testify if he is summoned. If he is not summoned, it is wajib for him to volunteer to testify byapproaching the Shariat judge with the information he has. If by not disclosing what he knows, a Muslim is harmed or loses his right, it is haraam to remain silent.

In short if a person is capable of helping the oppressed or prevent the oppressor from oppressing, it is wajib on him to do so.

It is not wajib to give evidence in a situation where not testifying does not cause any harm to a Muslim, nor does it deprive him of his right. In this case a person can even refuse to testify even if he is ordered to do so, because neither is he a direct witness to the dispute nor is his silence harmful in anyway.

Muhammad Ibne Muslim says, quoting an authentic tradition from Imam Muhammad al-Baqir (a.s.): "If one hears an evidence (i.e. he becomes a witness) but he had not been made a witness, then if he likes he can testify or he can prefer to remain silent." 
(Wasaelush Shia)

Testify only if you are certain

The witness is required to pay attention to all the aspects of the matter that he has witnessed and when he is testifying, he must only say that, about which he is certain. He must not mention those things, which he himself has not heard, or seen. It should be clear as the Sun, as mentioned in tradition.

When a true testimony will oppress someone

It should be known that a testimony should not endanger the life, property or honour of a Muslim. It should also not pose a threat to the life, property and honour of the witness. It is wajib to give evidence and haraam to conceal it so that justice is established in the society and injustice is eradicated. The oppressor ought to be punished and the right may be restored to its owner but if the testimony itself becomes the cause of oppression it is not wajib to testify. Rather it is haraam to do so and it is wajib to conceal evidence. For example if a person knows that if he testifies against a particular oppressor, the oppressor will take revenge on him or on his relatives or plunder his wealth, then it is wajib to conceal evidence. Similarly, there may be a situation where a debtor deep in debts is unable to clear his dues because of his poverty. At the same time he cannot prove his helplesness and the creditor is not prepared to spare him. In this case also it is wajib to conceal evidence, if the evidence given by a witness will cause the poor debtor to be oppressed.

The following traditions of our Masoomeen (a.s.) emphasise the justification of concealing evidence under special circumstances.

Hazrat Imam Musa al-Kazim (a.s.) says: 
"Give evidence for the sake of Allah even if you have to testify against yourself, your parents or your own relatives - But you must not cause harm to your believing brother by concealing evidence. However, if your believing brother is going to be oppressed, then do not testify." 
(Wasaelush Shia)

Dawood Ibne Hasan says that he heard Imam Ja'far as-Sadiq (a.s.) saying: 
"Give evidence for the sake of Allah, even if you have to testify against your parents or your own son. But do not give evidence to cause harm (Zaeer) to your believing brother."

The narrator says that, 'I asked, "What is Zaeer?" He (a.s.) said, 
"It is when someone who has a right, and in order to obtain it he resorts to oppression, contrary to the order of Allah and the Holy Prophet (s.a.w.s.). For example, a man is indebted to another, but the debtor is in straitened circumstances. In this situation, Allah has ordered that he must be given respite till he becomes self-sufficient. And (Allah) says, 
...then let there be postponement until (he is in) ease…

Now if in spite of this the creditor summons you to testify, and you know the poverty of the debtor, then it is not permitted for you to testify (that he has taken the loan)."
(Wasaelush Shia)