Musannaf Ibn Abi Shayba 3:748

Hafs narrated to us, from Muhammad ibn Qays, from al-Sha'bi, that he was asked about the Imam when he performs the taslim and then does not turn away [from the qibla]. He said: "Leave him until he finishes his innovation (bid'ah)." And he used to dislike that one should stand up and perform the remaining part of the prayer (qada).