Sahih Al Bukhari Hadith Number 1497

Narrated ‘Abdullah bin Abu Aufa : Whenever a person came to the Prophet (peace be upon him) with his alms, the Prophet (peace be upon him) would say, “O Allah! Send your Blessings upon so and so.” My father went to the Prophet (peace be upon him) with his alms and the Prophet (peace be upon him) said, “O Allah! Send your blessings upon the offspring of Abu Aufa.”

24  Obligatory Charity Tax (Zakat)
Hadith number 1497
Volume no 2
Chapter: 64 (The invoking and supplicating of the Imam for the one who gives in charity)