Allah, the Exalted, says (in Surah At-Tawbah): "Take alms from their wealth in order to purify them and sanctify them with it, and pray for them. Verily, your prayer is a source of security for them." Until the end of the verse.

Narrated 'Abdullah bin Abu Aufa: Whenever a person came to the Prophet with his alms, the Prophet would say, "O Allah! Send your Blessings upon so and so." My father went to the Prophet with his alms and the Prophet said, "O Allah! Send your blessings upon the offspring of Abu Aufa."