Turn to Allah with sincere repentance! (Surah At-Tahrim 66: 8)

O you who believe! Turn to Allah with sincere repentance! It may be that your Lord will expiate from you your sins, and admit you into Gardens under which rivers flow -- the Day that Allah will not disgrace the Prophet and those who believe with him. Their light will run forward before them and in their right hands. They will say: "Our Lord! Keep perfect our light for us and grant us forgiveness. Verily, You are Able to do all things.'' (Surah At-Tahrim 66: 8)


Encouraging sincere Repentance

Allah the Exalted said,

O you who believe! Turn to Allah with sincere repentance! meaning, a true, firm repentance that erases the evil sins that preceded it and mend the shortcoming of the repenting person, encouraging and directing him to quit the evil that he used to do. Allah said,

It may be that your Lord will expiate from you your sins, and admit you into Gardens under which rivers flow  And when Allah says, "it may be,'' it means He shall.

the Day that Allah will not disgrace the Prophet and those who believe with him meaning, on the Day of Resurrection, Allah will not disgrace those who believed in the Prophet (Sallallahu Alayhi wa Sallam),

Their light will run forward before them and in their right hands  as we explained in Surah Al-Hadid,

They will say:"Our Lord! Keep perfect our light for us and grant us forgiveness. Verily, You are Able to do all things.'' Mujahid, Ad-Dahhak and Al-Hasan Al-Basri and other said, "This is the statement that the believers will say on the Day of Resurrection, when they witness the light of the hypocrites being extinguished.'' Imam Ahmad recorded that a man from the tribe of Banu Kinanah said, "I prayed behind the Messenger of Allah (Sallallahu Alayhi wa Sallam) during the year of the Conquest (of Makkah), and heard him say,

O Allah! Please, do not disgrace me on the Day of Resurrection.''


Source: Tafsir ibn Kathir (Abridged)