Musannaf Ibn Abi Shayba 3:2042

Isma'il ibn 'Ulayyah narrated to us, from 'Abd al-'Aziz ibn Suhayb, that Anas ibn Malik sat in the third rak'ah, so they glorified Allah (said "SubhanAllah") to him. He stood up and completed them as four. When he performed the taslim, he prostrated two prostrations, then he turned his face toward the people and said, "If you make a mistake, do like this."