Of their goods, take alms, that so thou mightest purify and sanctify them; and pray on their behalf. Verily thy prayers are a source of security for them: And Allah is One Who heareth and knoweth. At-Tawbah 9:103 ⧉
Tafsir:
The proof of sincere repentance is a greater urge to serve the cause of religion. To absolve themselves of sin, they offered a part of their cherished property for the cause of God. On seeing such a positive response from them, the Prophet was asked not to reproach them but rather to give them psychological support, pray for them so that the burden (of guilt) in their hearts was lightened and their confidence in their faith restored. Doing wrong is not the real evil in the eyes of God; persistence in that wrong is the real evil. One who begins to justify his wrongs ruins himself, while one who admits his mistakes and tries his best to atone for them with good deeds is worthy of being pardoned by God.