Musannaf Ibn Abi Shaybah 98 — Running the fingers through the beard

Hassan bin Bilal said: I saw Sayyiduna Ammar bin Yasir (may Allah be pleased with him) pass his fingers through his beard (khilal) in ablution, and I asked him the reason for it. He said: I saw the Messenger of Allah (peace and blessings be upon him) do just the same.