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 kabbalistic (mystical) interpretation of Genesis 17:24: and classical mystical sources.