Musnad Ahmad 1153:2286

Ya'qub narrated to us, he said: My father narrated to us, from Ibn Ishaq, he said: Abdullah ibn Abi Bakr ibn Muhammad narrated to me, from 'Amrah bint 'Abd al-Rahman, from 'Aisha, she said: "Ibrahim, the son of the Messenger of Allah, passed away while he was eighteen months old, and he did not perform the funeral prayer over him."