Musnad Ahmad 33:1058

'Abd al-Razzaq narrated to us, Sufyan informed us, from Abu al-Zubayr, from Jabir, who said: The Prophet, peace and blessings of Allah be upon him, sent me for a need. I came while he was praying facing the east, and he was gesturing with a gesture on his riding beast; the prostration was lower than the bowing. I greeted him, but he did not return the greeting to me. He said: When he finished his prayer, he said: "What did you do regarding such and such need? For I was praying."