Musnad Abu Ya'la al-Mawsili 42:425

From Abu Sa’id al-Khudri, that the Messenger of Allah (may Allah bless him and grant him peace) said: "Perhaps a man earns wealth from a lawful source, so he feeds himself. And a man who has wealth in which there is charity, so he says: 'O Allah, send blessings upon Muhammad, Your servant and Your Messenger, and send blessings upon the believing men and the believing women, and the Muslim men and the Muslim women.' For indeed, it is a purification for him."