Narrated Asma' bint Abu Bakr:

I conceived `Abdullah bin AzZubair at Mecca and went out (of Mecca) while I was about to give birth. I came to Medina and encamped at Quba', and gave birth at Quba'. Then I brought the child to Allah's Messenger (ﷺ) and placed it (on his lap). He asked for a date, chewed it, and put his saliva in the mouth of the child. So the first thing to enter its stomach was the saliva of Allah's Messenger (ﷺ) . Then he did its Tahnik with a date, and invoked Allah to bless him. It was the first child born in the Islamic era, therefore they (Muslims) were very happy with its birth, for it had been said to them that the Jews had bewitched them, and so they would not produce any offspring.

حَدَّثَنَا إِسْحَاقُ بْنُ نَصْرٍ، حَدَّثَنَا أَبُو أُسَامَةَ، حَدَّثَنَا هِشَامُ بْنُ عُرْوَةَ، عَنْ أَبِيهِ، عَنْ أَسْمَاءَ بِنْتِ أَبِي بَكْرٍ ـ رضى الله عنهما ـ أَنَّهَا حَمَلَتْ بِعَبْدِ اللَّهِ بْنِ الزُّبَيْرِ بِمَكَّةَ قَالَتْ فَخَرَجْتُ وَأَنَا مُتِمٌّ، فَأَتَيْتُ الْمَدِينَةَ فَنَزَلْتُ قُبَاءً فَوَلَدْتُ بِقُبَاءٍ، ثُمَّ أَتَيْتُ بِهِ رَسُولَ اللَّهِ صلى الله عليه وسلم فَوَضَعْتُهُ فِي حَجْرِهِ، ثُمَّ دَعَا بِتَمْرَةٍ فَمَضَغَهَا، ثُمَّ تَفَلَ فِي فِيهِ فَكَانَ أَوَّلَ شَىْءٍ دَخَلَ جَوْفَهُ رِيقُ رَسُولِ اللَّهِ صلى الله عليه وسلم ثُمَّ حَنَّكَهُ بِالتَّمْرَةِ، ثُمَّ دَعَا لَهُ فَبَرَّكَ عَلَيْهِ، وَكَانَ أَوَّلَ مَوْلُودٍ وُلِدَ فِي الإِسْلاَمِ، فَفَرِحُوا بِهِ فَرَحًا شَدِيدًا، لأَنَّهُمْ قِيلَ لَهُمْ إِنَّ الْيَهُودَ قَدْ سَحَرَتْكُمْ فَلاَ يُولَدُ لَكُمْ‏.‏