Allah (SWT) Most High says in Noble Qur'an, "Ask your Lord for forgiveness and then turn in repentance to Him..." (11:3)
Also Allah (SWT) Most High says in Noble Qur'an, "O you who believe! Turn (in repentance) to Allah with sincere repentance; Perhaps your Lord will remove your evil from you... “(66:8)
It should not be forgotten that we, being human beings are prone to committing sins. Sinless are nobody in the universe except the Masumeen and the Noble Prophet Muhammad (saw). To seek pardon from Allah (SWT) is the instant remedy for every problem. Once a person came to Imam Ali (A.S) and asked him for the solution of repaying the debts, Imam Ali (A.S) was told to do repentance (Tawbah) and seek repentance from Allah (SWT). The other person came asking for the remedy of a sickness; Imam Ali (A.S) was prescribed the same repentance (Tawbah) and seeks repentance from Allah (SWT). Yet another person came asking for the bestowing of an offspring from Allah (SWT) and Imam Ali (A.S) was also told to do Istighfar (repenting) as much as possible.
The Noble Prophet Muhammad (saw) said: "The sign of the people of Hell is mostly because of the postponement of repenting (Tawbah and Istighfar)."
The Noble Prophet Muhammad (saw) said: "A sincere repentant never sins again as the milk drawn from the breast never can go back to its source."
The Noble Prophet Muhammad (saw) said: "The repentant from a sin is as same as him who did not commit it."
The Noble Prophet Muhammad (saw) said: "Nothing is more favorable to Allah (SWT) than a male or female repentant believer."
The Noble Prophet Muhammad (saw) said: "There are four signs of one who is repentant: (1) He is sincere to Allah (SWT) in his actions (2) He shuns falsehood (3) He is firmly attached to truth and (4) He is eager to do good."
Imam Ali (A.S) said: "The sin that makes you sad and repentant is more liked by Allah (SWT) than the good deed which turns you arrogant."
Imam Ali (A.S) said: "A sincere repentant: (1) is ashamed of his past sins (2) takes up the duties overlooked and fulfils them (3) makes good the willfully ignored conditions of a trust managed by him (4) forgives those who provoke him (5) does not demand repayment of loans from those who are in financial distress (6) makes firm determination not to sin ever again (7) surrenders his self to the adoration, devotion and service of Allah (SWT) when it had swelled to the point of exploding due to inordinate consumption of worldly pleasures, transgression and disobedience."
Imam Zainul Abideen (sajjad) (A.S) said: "My God! You are He who has opened a door to your pardon and named it 'repentance' for you said, 'Repent to God with unswerving (sincere) repentance' (66:8). What is the excuse for him who remains heedless of entering the door after its opening?"
Imam Jafar Sadiq (A.S) said: "If a servant repents sincerely, Allah (SWT) loves him (and) so conceals his sins."
Repentance is the cord of Allah (SWT) which those repenting must necessarily grasp; they need to clean their interior of their sins and testify against themselves before their Lord.
They should be repentant from the depths of their hearts with regards to their past misdeeds, and fearful with regards to the remaining period of their lives. The Friends of Allah (SWT) repent for the (inappropriate) thoughts that may have passed through their minds, while the special ones repent for engaging themselves in anything other than Allah (SWT), even A.S the general masses repent for the sins committed by them.
It is vital that, in order to make amends for past deeds and refrain from committing sins in the future, the person repenting should not look upon any sin as being trivial and insignificant, but should always experience regret over his past lapses, keep his soul away from various kinds of lust and guide it towards struggle (against lust) and worship.
Allah (SWT) loves a believer who seeks forgiveness by asking for repentance and Istighfar. Repentance (Tawbah) is among the most praiseworthy acts of virtue for the believers.
Allah (SWT) is more pleased with the repentance of His servants than a person who found his lost camel in a waterless desert. In fact, Allah (SWT) loves to see the believer repent more than He hates to see him sin.
Allah (SWT) accepts the repentance of a believer for as long as he is not at the point of death. He (or she) who repents of a sin is like him who has committed no sin. Indeed Allah (SWT) loves a believing servant who sins and then realizes his mistake and greatly repents with a true heart and seeks His forgiveness, mercy, and intends with a true heart to never repeat the sin.
When a believer commits a sin and seeks forgiveness (Tawbah), Allah (SWT) becomes so happy and says: "My servant committed a sin and then he came to realize that he has a Lord who holds the sinner responsible and accountable, and also that He has a Lord who forgives the sins if asked for forgiveness: So let him be forgiven."
Believers are on a path of continual improvement. People do make mistakes, but believers analyze their mistakes and take positive actions to correct them. This examination is critical for creating purity in every action. In this way, believers develop a lifestyle which is firmly grounded in the principles of faith, and as loved by Allah (SWT) and His Noble Prophet Muhammad (saw). All the sons of Adam are sinners, but the best of sinners are those who repent.
source : sibtayn
