There are many traditions that support the taking of a false oath in order to save the Muslims. For example, Shaykh Ansari in his book, Makasib quotes from Imam Ja'far as-Sadiq (a.s.) and Imam Ali (a.s.) that they have narrated the following tradition of the Holy Prophet (s.a.w.s.).
The Holy Prophet (s.a.w.s.) says:
"Swear falsely by Allah, but save your Muslim brothers from unjust murder."
Ismael Ibne Saad records a confirmed tradition, wherein he says that he asked Imam Ali Reza (a.s.) concerning the person who takes a false oath to save his property from an unjust ruler.
Imam Reza (a.s.) replied,
"There is no harm (in it)."
He was again asked, "If a man takes a false oath to save the property of his believing brother, just as he had sworn falsely to save his own property. Is it allowed?"
Imam (a.s.) said,
"Yes! It is allowed."
(Wasaelush Shia)
Also Hazrat Imam Ja'far as-Sadiq (a.s.) says,
"If one is compelled to take a false oath to save the life of a Muslim or to save his property from an oppressor or a thief, not only is the expiation of this false oath not payable but he would rather be eligible for (divine) rewards."
Monetary loss and falsehood
Two points must be remembered at this juncture. One is that even though it is permitted to lie to save oneself from every type of monetary loss, yet it is Mustahab (recommended) not to lie if one is capable of bearing the loss. Amirul Momineen Ali (a.s.) says,
"The sign of belief is that one speaks the truth even if it causes loss and refrains from a lie even if it is beneficial (to lie)."
(Nahjul Balagha)
If one is compelled he must limit himself to Toriya
Another important point is that in situations where the Mujtahids have permitted Toriya it is best not to use falsehood, but limit oneself to Toriya only.
Reconcile two believing people by using falsehood
Imam Ja'far as-Sadiq (a.s.) said:
"Speech is of three types, truth, falsehood and reconciling people."
Someone asked, "May my life be sacrificed for you. What is, 'reconciling people'?"
Imam (a.s.) replied:
"You hear someone speaking ill about somebody but you tell the other person that the former was saying good things about you."
(Wasaelush Shia)
Conveying a message of ill will
Infact one is ordered to resort to lies if by doing so, one can bring about reconcillation between two people. One who brings about such reconciliation shall not be termed a liar. Because if the message of ill will is communicated from one to other, it will only increase enmity between the two.
In the same way if a husband and wife have separated and divorce is about to take place, one is allowed to speak a lie if it can bring about a reunion. For example the husband could be told, "Your wife is very much troubled by the separation. She has such intense feelings for you that she may fall ill." Or the wife may be told similar things so that they may reunite.
Reconciliation among people
The Holy Prophet (s.a.w.s.) has said,
"After the fulfillment of wajib acts, the best action is to bring about peace and reconciliation among people. This is such an act that spreads goodness in the world."
Amirul Momineen Ali (a.s.) said that the Holy Prophet (s.a.w.s.) has said at the time of recording his will and testament.
"O Ali, Allah even likes a falsehood for the sake of peace and dislikes truth that spreads corruption."
(Wasaelush Shia)
The Holy Prophet (s.a.w.s.) has also said,
"To make peace among people and to think about reconciling people, and removing discord is better than prayers and fasting."
Abu Hanifa Saeq Al Haj says, "There was an inheritance dispute between my son-in-law and me. Our dispute was in process when the agent of Imam as-Sadiq (a.s.), Mufazzal happened to pass by. He stopped to listen for a while then returned to his house. He then gave us four hundred dirhams and solved the dispute.
Then he said, 'The money that I gave you was not mine. It belonged to my master Imam Ja'far as-Sadiq (a.s.). He had ordered me to solve the disputes among his followers through this money.'"
This shows the importance of peace and reconciliation. The Holy Prophet (s.a.w.s.) has also stated that it was better than prayers and fasting, even though this action is Mustahab (recommended) whereas the former are Wajib (Obligatory). The reason for this could be that due to prayers and fasting an individual is reformed. Whereas the peacemaker reforms the whole society and consequently prayers and fasting also become popular among the people. Unity among the Muslims is not only beneficial for the Hereafter, it is very much needed from the worldly point of view also. When the hearts of the believers unite for the sake of Allah, such a power is achieved that not only the apparent enemies can be faced but even the hidden enemies, i.e. "the self" and "shaitan", can be easily deflected.
Kur water and the united hearts
The unity and understanding among the people could be compared to Kur water. If water is divided by putting it in different vessels and each of them is less then a kur, then whenever impurity (Najasat) falls into one of them, it makes that water Najis (impure). But if all the water is collected in one place and it becomes more than a kur and if an impurity falls into it, it does not make the kur water Najis. On the contrary the kur water is capable of purifying the impurity of a Najis object. Exactly, in the same way when the people unite together, the divine mercy descends upon them and each one benefits by it. Secondly due to the unity among the Muslims they will be held in high esteem by people of different faiths.
Another example is the merits of congregational prayers and its great rewards. It is very much recommended to behave kindly towards the believing brother, to help him and support him. Similarly it is highly meritorious to visit the believers, to shake hands with them and to hug them. These actions carry great benefits. To make peace between two believers qualifies one to untold rewards. Similarly it is mentioned that to befriend a believer for the sake of Allah carries tremendous rewards. After examining the rewards for all of the above actions one concludes that all such actions have been promulgated for maintaining the unity among believers.
Falsehood in the battle-field
It is known from some traditions that during a war with unbelievers, it is permissible to use falsehood, if by doing so, victory can be gained over them.
Promise to a wife
A man can give a promise to his wife even if he does not intend to fulfill it, a man can give a false promise to fulfill his wife's desire, if he thinks that his refusal will cause dispute and discord in the family, or make his wife extremely unhappy. Obviously such falsehood is also permissible under compelling conditions when a man fears that refusing to promise may lead to an extreme situation like divorce.
However, whether such a promise is permitted or not is difficult to confirm. Some weak traditions do state that such a false promise is allowed. For example if a wife asks for something, her husband can give her a false promise.
Fear of retribution and good deeds
Hazrat Ali Ibne Abi Talib (a.s.) says:
"Avoid lying! For when one desires something he strives for it and when one fears something he strives to keep it away from himself."
(Al Kafi)
Imam Ali (a.s.) explains the above tradition as follows: If one sincerely desires the pleasure of Allah one must strive for it and one of the ways of doing so is by refraining from lies. Falsehood is a forbidden act causing extreme displeasure of Allah. In the same way if one really fears divine retribution, one must keep aloof from sins, for sins incur punishment. If a person merely claims that he hopes for divine rewards and fears divine punishment, but does not perform good deeds nor refrain from sins, he is a liar.
The following saying of Amirul Momineen Ali (a.s.) is recorded in Nahjul Balagha:
"One who thinks that he hopes (in divine rewards) but his actions do not express it, then by Allah, he is a liar. For when he hopes for something it becomes apparent from his actions.
But if he hopes in Allah and his actions do not show it? In the same way when one is afraid of something his actions express this (fear) and he flees from that thing. Then after claiming to be fearful of divine punishment why does he not flee from sins?"
Thus if a person who claims to be fearful of Allah and hopeful of divine rewards, but whose actions do not confirm his claim, is considered a liar. In the same way a person who claims to have the traits of patience, thankfulness, contentment and resignation etc. which are not shown in his behaviour is also a liar.
Your speech must conform to your thoughts
Hazrat Imam Ja'far as-Sadiq (a.s.) says,
"Whenever you say 'Allaho-Akbar' (Allah is the greatest) you must consider everything between the earth and the sky to be lesser than Allah. Because when Allah sees that a person say Allaho-Akbar only superficially, He says, 'O liar! You try to be smart with Me? By My Might and Honour I shall deprive you of My remembrance.'"
It is regretful that people verbally say, 'Allaho Akbar' but their actions belie their words. For if they are told to do something for the sake of Allah or to refrain from something for the sake of Allah they do not pay any heed, but if a monetary fine is due for any disobedience, they are sure to respond. Thus money has importance for them than Allah's pleasure or displeasure. There are people who perform particular actions or restrain from them only due to fear of harm by fellow humans. If they are told to do so only due to the fear of Allah, they will not be impressed.
A show of submission
A person who says to Allah, 'Thee only do we worship and Thee only we ask for help', but his actions are such that day and night he is involved in the acquisition of wealth and is preoccupied in the satisfaction of carnal desires. Can we consider this man to be truthful? Does this man really worship Allah?
In the same way many a man puts his trust and faith in the apparent agencies through which he gets his profit and gain. He regards these as the deciding authorities and seeks their help, overlooks the fact that these means themselves are through Allah's grace. Can such a person be truthful when he says "Thee only do we worship and Thee only we ask for help?"
Falsehood in supplications
Oftentime people supplicate with the following words, "I am pleased with my Lord and Cherisher, He the sole cherisher of all the creatures. I am satisfied with Him."
But if the situation changes and these people are faced with distressing circumtances, they do not hesitate to complain about what Allah has decreed for them. In such a case the above-mentioned supplication amounts to lying.source : GREATER SINS by Ayatullah-ul-Uzma Sayed Abdul Husain Dastghaib Shirazi (r.a.)