Musnad Ahmad 32:852

Mu'ammal and 'Affan narrated to us, they said: Hammad narrated to us, Thabit narrated to us, from Anas, who said: I set out with 'Abdullah ibn Abi Talhah to the Messenger of Allah (peace and blessings of Allah be upon him) when he was born. I came to the Prophet (peace and blessings of Allah be upon him) while he was in a cloak, smearing a camel of his [with tar]. He said to me: "Do you have dates with you?" I said: "Yes." He took some dates and put them in his mouth, then he chewed them, then he performed *tahnik* [rubbed them on the palate of the infant]. The boy opened his mouth, so he put them into the boy's mouth. The boy began to smack his lips. The Messenger of Allah (peace and blessings of Allah be upon him) said: "The Ansar refuse [to love anything] except the love of dates." And he named him 'Abdullah.