Musnad Abu Ya'la al-Mawsili 7:13

Muhammad ibn 'Abbad al-Makki narrated to us, Hatim ibn Isma'il narrated to us, from Muhammad ibn 'Uthman, from Ibn Abi Sandar al-Aslami, from a freed slave of 'Abd al-Rahman ibn 'Awf, who said: 'Abd al-Rahman said: "I was standing in the courtyard of the mosque when I saw the Messenger of Allah (ﷺ) coming out from the gate that is adjacent to the graveyard. I waited for a while, then I went out following him. I found that he had entered a garden of the As-waf (a place in Medina). The Messenger of Allah (ﷺ) performed ablution, then he prayed two rak'ahs. He performed a prostration and prolonged the prostration in it. When the Messenger of Allah (ﷺ) finished the tashahhud, I approached him and said: 'May my father and mother be sacrificed for you, you performed a prostration and I feared that Allah might have taken your soul due to its length.' He said: 'Indeed, Gabriel gave me glad tidings that whoever sends blessings upon me, Allah will send blessings upon him, and whoever sends peace upon me, Allah will send peace upon him.'"