Musnad Ahmad 370:1

Hassan ibn Musa narrated to us, he said: Hammad ibn Salamah narrated to us, from al-Azraq ibn Qays, from Yahya ibn Ya'mar, from a man among the companions of the Prophet, may Allah bless him and grant him peace, who said: The Messenger of Allah, may Allah bless him and grant him peace, said: "The first thing for which the servant will be brought to account is his prayer. If he completed it, it is recorded for him as complete. If he did not complete it, Allah, the Almighty and Majestic, says: 'Look, do you find any voluntary acts for My servant, so that you may complete his obligatory acts with them?' Then the Zakat is likewise, then the deeds are taken according to that."