Musannaf Ibn Abi Shaybah 3134 — What a man says when he finishes

Al-A'mash said: Ibrahim was asked: "If the imam, after giving the salam, says 'Salla Allahu ala Muhammad' (may Allah send blessings upon Muhammad) or 'wa la ilaha illa Allah' (and there is no god but Allah), what is the ruling?" He said: "The early generations did not do this."