Musnad Ahmad 1015:4

Waki’ narrated to us, ‘Abd al-Hamid ibn Bahram narrated to me, from Shahr ibn Hawshab, from ‘Abd al-Rahman ibn Ghanm, who said: Abu Malik al-Ash’ari said to his people: "Shall I not pray for you the prayer of the Messenger of Allah, may Allah bless him and grant him peace?" So he arranged the men in rows, then he arranged the children in rows behind the men, then he arranged the women in rows behind the children.