Musannaf Ibn Abi Shayba 3:581

Abu Khalid al-Ahmar narrated to us, from Muhammad ibn ‘Ajlan, from ‘Ali ibn Yahya ibn Khallad, from his father, from his uncle—and he was a Badr-warrior—who said: We were sitting with the Messenger of Allah, may Allah bless him and grant him peace, when a man entered and prayed a light prayer, not completing its bowing nor its prostration, while the Messenger of Allah, may Allah bless him and grant him peace, was watching him, and we were unaware. He said: So he prayed, then came and greeted the Prophet, may Allah bless him and grant him peace. He said: "Repeat, for you have not prayed." He did that three times, and each time he said to him: "Repeat, for you have not prayed." When it was the fourth time, he said: "O Messenger of Allah, teach me, for by Allah, I have exerted my effort." He said: "When you stand for prayer, face the Qibla, then say the Takbir, then recite, then bow until you are at ease while bowing, then rise until you are at ease while standing, then prostrate until you are at ease while prostrating, then sit until you are at ease while sitting. If you do that, your prayer is complete, and whatever you diminish from that, you have diminished from your prayer."