וְאַ֨בְרָהָ֔ם בֶּן־תִּשְׁעִ֥ים וָתֵ֖שַׁע שָׁנָ֑ה בְּהִמֹּל֖וֹ בְּשַׂ֥ר עָרְלָתֽוֹ׃
And Abraham was ninety years old and nine, when he was circumcised in the flesh of his foreskin.
Read Jewish philosophical commentary on Genesis 17:24: and classical philosophical sources.