Musannaf Ibn Abi Shayba 3:746

Hushaym narrated to us, he said: Mansur and Khalid informed us, from Anas ibn Sirin, he said: I said to Ibn Umar: "I am preceded by some of the prayer, so the Imam gives the taslim, and I stand up and complete what I was preceded by, or should I wait for him to turn?" Ibn Umar said: "The Imam, when he gave the taslim, would stand up." And Khalid said: "The Imam, when he gave the taslim, would turn away." The turning away was with the taslim.