Muwatta Malik 106

Arabic

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يَقُولُ إِذَا جَاوَزَ الْخِتَانُ الْخِتَانَ فَقَدْ وَجَبَ الْغُسْلُ ‏.‏

Translation

Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to say, "When the circumcised part passes the circumcised part, ghusl is obligatory

Authenticity

Sahih · Salim al-Hilali

Reference