Musnad Abu Ya'la al-Mawsili 160:228

Ubayd Allah ibn Umar narrated to us, Yahya ibn Sa’id narrated to us, he said: Muhammad ibn ‘Ajlan narrated to me, he said: Ali ibn Yahya ibn Khallad narrated to me, from his father, from his uncle—and he had witnessed Badr—he said: We were with the Messenger of Allah, may Allah bless him and grant him peace, in the mosque, when a man entered and prayed. The Messenger of Allah, may Allah bless him and grant him peace, began to watch him. 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, returned the greeting, then said: "Go back and pray, for you have not prayed." So he went back and 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, returned the greeting, then said: "Go back and pray, for you have not prayed." He did that two or three times. Then he said to him, in the second or third time: "O Messenger of Allah, I have exhausted myself, so teach me and show me." The Messenger of Allah, may Allah bless him and grant him peace, said to him: "When you intend to pray, perform wudu and perfect your wudu, then face the qibla, then say takbir, then recite, 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 at ease while sitting, then prostrate until you are at ease while prostrating, then rise until you are at ease while sitting. If you complete your prayer in this manner, then you have completed it; and whatever you diminish from that, you only diminish it from your prayer."