Sahih Muslim Book 25, Hadith Number 5341.

Chapter : The Excellence of Tahnik of the new-born child at the time of its birth and of carrying it to a pious person so that he may soften some dates and rub its palate with them, and permissibility of giving name on the day of its birth and the excellence of such names as ‘Abdullah, Ibrahim and the names of all the apostles of Allah (may peace be upon him).

Anas b. Malik reported that the son of Abu Talha had been ailing. Abu Talha set out (on a journey) and his son breathed his last (in his absence). When Abu Talha came back, he said (to his wife): What about my child? Umm Sulaim (the wife of Abu Talha) said: He is now in a more comfortable state than before. She served him the evening meal and he took it. He then came to her (and had sexual intercourse with her) and when it was all over she said: Make arrangements for the burial of the child. When it was morning. Abu Talha came to Allah’s Messenger (may peace be upon him) and informed him, whereupon he said: Did you spend the night with her. He said: Yes. He (the Holy Prophet) then said: O Allah, bless both of them (and as a result of blessing) she gave birth to a child. Abu Talha said to me (Anas b. Malik) to take the child, (so I took him) and came to Allah’s Messenger (may peace be upon him). She (Umm Sulaim) also had sent some dates (along with the child). Allah’s Apostle (may peace be upon him) took him (the child) (in his lap) and said: Is there anything with you (for Tahnik). They (the Companions) said: Yes. Allah’s Apostle (may peace be upon him) took hold of them (dates and chewed them). He then put them (the chewed dates) in the mouth of the child and then rubbed his palate and gave him the name of ‘Abdullah.