Musnad Ahmad 658:233

Yahya narrated to us, Sufyan narrated to us, Sulayman narrated to me, from Muslim Abu al-Duha, from al-Bara’ who said: Ibrahim, the son of the Messenger of Allah (may Allah bless him and grant him peace)—or a son of his—died at sixteen months old, while he was still nursing. Yahya said: I believe it was Ibrahim (peace and blessings be upon him). The Prophet (may Allah bless him and grant him peace) said: "Indeed, he has a wet nurse who will complete his nursing in Paradise."