Musnad Ahmad 5:168

Waki’ narrated to us, Fitr narrated to us, from Mundhir, from Ibn al-Hanafiyyah, who said: Ali said, "O Messenger of Allah, what do you think if a child is born to me after you; shall I name him with your name and give him your kunyah?" He said, "Yes." So it was a concession from the Messenger of Allah, may Allah bless him and grant him peace, for Ali.