Ayesha reported,

She said, "The first child born in Islam was Abdullah bin Zubayr. They brought him to the Prophet ﷺ, who took a date, chewed it softly, and then placed it in the child's mouth. So the first thing to enter his stomach was the saliva of the Prophet ﷺ."In another narration, "We brought Abdullah bin Zubayr to the Prophet ﷺ for him to perform tahnik. We searched for a date, and it was difficult to find one."

عن عائشة زوج النبي ﷺ

قالت: أول مولود في الإسلام عبد الله بن الزبير، أتوا به النبي ﷺ، فأخذ النبي ﷺ تمرة فلاكها، ثم أدخلها في فيه، فأول ما دخل بطنه ريق النبي ﷺ. وفي رواية: جئنا بعبد الله بن الزبير إلى النبي ﷺ يحنكه، فطلبنا تمرة، فعز علينا طلبها.