Musnad Abu Ya'la al-Mawsili 160:227

Ubayd Allah al-Qawariri narrated to us, Yahya bin Sa'id narrated to us, from Ubayd Allah bin Umar, who said: Sa'id bin Abi Sa'id narrated to me, from his father, from Abu Hurayrah, that a man entered the mosque while the Prophet, may Allah bless him and grant him peace, was in the mosque. He prayed, then came to the Messenger of Allah, may Allah bless him and grant him peace, and greeted him. The Messenger of Allah, may Allah bless him and grant him peace, said to him: "Go back and pray, for you have not prayed." He repeated that three times. He said: "O Messenger of Allah, I do not know better than this, so teach me." The Messenger of Allah, may Allah bless him and grant him peace, said to him: "When you intend to pray, say the takbir (Allahu Akbar), then recite what is easy for you of the Quran. Then bow until you are at ease while bowing, then rise until you are standing upright, then prostrate until you are at ease while prostrating, then rise until you are sitting upright. Then do this in all of your prayer."