In the Qur’an

And all of you beg Allah to forgive you all, O believers, that you may be successful. (Qur’an, 24:31)

“And (commanding you): “Seek the forgiveness of your Lord, and turn to Him in repentance.” (Qur’an, 11:3)

“O you who believe! Turn to Allah with sincere repentance!” (Qur’an, 66:8)

In the Sunnah

Prophet Muhammed (peace be upon him) said: “Allah is my witness, that I seek His forgiveness and turn to Him more than 70 times a day.” (Al-Bukhari)

“Allah is more pleased with the repentance of His servant than would be one of you who were to lose his camel in a barren desert and then find it suddenly.” (Al-Bukhari and Muslim)

“Allah will continue to hold out His Hand at night so that he who has sinned during the day might repent, and to hold out His hand during the day so that one who has sinned at night might repent, and Allah will continue to do so till the sun rises from the west (i.e. till the Day of Resurrection).”

“Allah, the Lord of honor and glory will accept repentance of His servant till his agony of death.” (Al-Tirmidhi)