Musannaf Ibn Abi Shayba 3:669

Yahya ibn Adam narrated to us, he said: Zuhayr narrated to us, from Abu Ishaq, from Abd al-Rahman ibn al-Aswad, from Alqama and al-Aswad, from Abdullah, he said: The Messenger of Allah (may Allah bless him and grant him peace) used to perform the taslim to his right and to his left, and Abu Bakr and Umar.