Musnad Ahmad 32:240

Waki’ narrated to us, Hammam narrated to me, from Ghalib—Waki’ said it this way: Ghalib, though it is actually Abu Ghalib—from Anas, that a funeral of a man was brought to him, so he stood at the head of the bier. Then a funeral of a woman was brought to him, so he stood lower than that, parallel to the middle of the bier. When he had prayed, Al-‘Ala’ ibn Ziyad said to him: "O Abu Hamzah, is this how the Messenger of Allah (peace and blessings of Allah be upon him) used to stand for the man and the woman, similar to what I saw you do?" He said: "Yes." Al-‘Ala’ ibn Ziyad then turned to us and said: "Memorize this."