Musannaf Ibn Abi Shaybah 3086 — Those who used to give two salams

Yazid bin Abi Ziyad said: Ibrahim gave the salam to the right and said 'As-salamu alaykum wa rahmatullah' (Peace be upon you and the mercy of Allah), saying it aloud; then he gave the salam to the left and said 'As-salamu alaykum wa rahmatullah', in a lower voice than the first.