Musnad Abu Ya'la al-Mawsili 3:79

Ubayd Allah narrated to us, Sufyan narrated to us, from Layth, from Mujahid, who said: A funeral procession passed by Ali. Some people stood up, so he said: "What is this?" They said: "Abu Musa." Ali said: "The Messenger of Allah (peace and blessings of Allah be upon him) stood up once, then he did not stand up [after that]."