Sahih al-Bukhari 4635
In-book no 4635وَعَنْ عُقْبَةَ بْنِ صُهْبَانَ، قَالَ سَمِعْتُ عَبْدَ اللَّهِ بْنَ الْمُغَفَّلِ الْمُزَنِيِّ، فِي الْبَوْلِ فِي الْمُغْتَسَلِ.
`Abdullah bin Al-Mughaffal Al-Muzani also said: "The Prophet (ﷺ) also forbade urinating at the place where one takes a bath."