Narrated Aisha:

The first child who was born in the Islamic Land (i.e. Medina) amongst the Emigrants, was 'Abdullah bin Az-Zubair. They brought him to the Prophet. The Prophet took a date, and after chewing it, put its juice in his mouth. So the first thing that went into the child's stomach, was the saliva of the Prophet

حَدَّثَنَا قُتَيْبَةُ، عَنْ أَبِي أُسَامَةَ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ ـ رضى الله عنها ـ قَالَتْ أَوَّلُ مَوْلُودٍ وُلِدَ فِي الإِسْلاَمِ عَبْدُ اللَّهِ بْنُ الزُّبَيْرِ، أَتَوْا بِهِ النَّبِيَّ ﷺ فَأَخَذَ النَّبِيُّ ﷺ تَمْرَةً فَلاَكَهَا ثُمَّ أَدْخَلَهَا فِي فِيهِ، فَأَوَّلُ مَا دَخَلَ بَطْنَهُ رِيقُ النَّبِيِّ ﷺ.