Musnad Ahmad 26:520

Abu Nu'aym narrated to us, Isra'il narrated to us, from Mukhariq al-Ahmasi, from Tariq ibn Shihab, who said: I heard Ibn Mas'ud saying: I witnessed an event with al-Miqdad ibn al-Aswad — another narrator said: a scene — that for me to be the one who did it would be more beloved to me than anything that could be equated to it. He came to the Prophet, peace and blessings of Allah be upon him, while he was supplicating against the polytheists, and he said: We will not say to you as the people of Musa said: "Go, you and your Lord, and fight; indeed, we are sitting right here." Rather, we will fight to your right, to your left, from before you, and from behind you. I saw the face of the Messenger of Allah, peace and blessings of Allah be upon him, brighten, and that pleased him.