Musnad Ahmad 658:83

Ibn Numayr narrated to us, al-A‘mash informed us, from Muslim ibn Sabih, al-A‘mash said: I think it is from al-Bara’ ibn ‘Azib, he said: Ibrahim, the son of the Messenger of Allah, peace and blessings of Allah be upon him, died while he was sixteen months old. The Messenger of Allah, peace and blessings of Allah be upon him, ordered that he be buried in al-Baqi‘. And he said: "Indeed, he has a wet nurse who will nurse him in Paradise."