The Messenger of Allah said, "All children of Adam do commit sins and the best of the sinners are those who repent." 
Man by nature is weak; he is weak in his aim and resolution and is unable to bear the consequences of his sins and misdeeds. So Allah out of kindness makes matters easy for man and He prescribed for him repentance.
The essence of repentance is to abandon the sin because of its ugliness – out of fear for Allah– and out of desire for His Mercy; to regret over what one has done, to determine not to go back to the sin again and to spend whatever is left of one's life in good deeds. As you can see, repentance is a deed of the heart that is pure between the slave and his Lord. It is neither a hard nor difficult job for him; it is just a deed of the heart, to abandon the sin, and not to go back to it. There are, in abstention from all that Allah forbid, well-being and peace of mind.
You do not need to repent at the hand of a man who will reveal your secret and manipulate your weakness. It is only a communication between you and your Lord; you seek His forgiveness and guidance and He forgives you. There is nothing like inherited sin in Islam, nor is there anything like an expected mankind saviour. Islam, is as discovered by the Austrian Jewish revert to Islam, Muhammad Asad who said, "I could not find it anywhere in the Qur'aan any mention of man's need for salvation. In Islam, there is no concept of the first inherited sin that stand between man and his fate, because 'Man can have nothing but what he does (good or bad). Islam does not require from man to present a sacrifice or kill himself in order to have the door of repentance opened for him and to be saved from sins."Allah says,
"No burdened person (with sins) shall bear the burden (sins) of another."
Repentance has great benefits and impacts, some of which are:
1. It makes man know expansiveness of Allah's forbearance, and magnanimity in concealing his misdeeds. Had He willed, He would have hastened to punish him and disgraced him in front of people so that he would not be able to live comfortably with them. But Allah honoured him by concealing for him his sins, covered him by His forbearance and endowed him with energy, provision and sustenance.
2. It lets him know his real self, that it is inclined to evil and that whatever comes from it of sins, misdeeds or negligence is an indication from forbidden desires, and that, it cannot dispense of Allah – for even a twinkle of an eye – for its purification and guidance.
3. Allah prescribes repentance in order to seek with it the greatest causes of happiness for man, which is creating refuge with Allah and seeking His assistance; and also to bring about different kinds of supplication; showing one's submission, helplessness to Allah, showing one's love to Allah, one's fear of and hope in Him; then the soul moves closer to its Creator in a special way which will not occur to it without repentance and escaping to Allah.
4. It makes Allah forgive him his past sins. Allah says,
"Say (O Muhammad) to those who have disbelieved, if they cease (from disbelief) their past will be forgiven." 
5. It makes one's evil deeds turned to good ones. Allah says,
"Except those who repent and believe and do righteous deeds; for those, Allah will change their sins into good deeds, and Allah is Oft-forgiving, Most-Merciful." 
6. It enables him treat his fellow human beings when they do evil to him as he will love Allah to treat him as regards his own misdeeds and sins; for recompense is in accordance with the type of deed. So, if he treats people in this good manner, he will also be treated by Allah in the like manner and Allah will be kind to him regardless of his evil deeds and sins, just as he does with his fellow human beings.
7. It enables him to know that he is full of faults and defects; this will make him refrain from speaking about the faults of other people and will be preoccupied with reforming his own self instead of thinking about the faults of others. 
I would like to conclude this section with the story of a man who came to the Prophet and said, "O Messenger of Allah! I have not left any small or big sin but I had committed it."
The Messenger of Allah said, "Don't you testify that there is no other deity worthy of worship except Allah and that Muhammad is the Messenger of Allah?"
He asked him this question three times and the man answered each time, "Yes."
He then said, "your testimony has erased all that (you have committed of sins)" 
In another narration, the man came to the Prophet and said, "Tell me! If a man committed all sins but has not associated anything in worship with Allah, and yet did not leave any small or big sin uncommitted, can his repentance be accepted?"
The Prophet asked the man, "Have you embraced Islam?"
The man answered, "As for me, I testify that there is no deity worthy of worship except Allah, that He is One and has no partner and that you are the Messenger of Allah."
The Prophet said, "Yes! Do good deeds and refrain from evil ones, so that Allah may turn all those evil deeds to good ones for you."
The man said, "Even my acts of treachery and my sins?!"
The Prophet said, "Yes."
The man said, "Allahu Akbar (Allah is the Most-Great) and he kept on saying that until he disappeared."
Islam therefore erases whatever sin one might have committed and sincere repentance also erases whatever sin one might have committed as authentically reported from the Prophet.
 Ahmad, At-Tirmidhee and Ibn Maajah
 Al-Mufradaat fee ghareebil Qur'aan, p. 76, quoted freely.
 Al-Fawaaid by Ibn Al-Qayyim.
 An-Najm 53:39.
 Road to Islam by Muhammad Asad p. 140.
 An-Najm 53:38
 Al-Anfaal 8:38.
 Al-Furqaan 25:70
 Muftaahu daaris-sa'aadah, Vol. 1, p. 358-370.
 Reported by Aboo Ya'laa; At-Tabaraanee; and Al-Maqdisee
 Ibn Abee 'Aasim; At-Tabaraanee and Al-Bazzaar.
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