The Book of Purification
1/25. Chapter:
Squatting While Urinating In The House
Sunan an-Nasai
أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ أَنْبَأَنَا شَرِيكٌ، عَنِ الْمِقْدَامِ بْنِ شُرَيْحٍ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ، قَالَتْ مَنْ حَدَّثَكُمْ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم بَالَ قَائِمًا فَلاَ تُصَدِّقُوهُ مَا كَانَ يَبُولُ إِلاَّ جَالِسًا .
It was narrated that 'Aishah said: "Whoever tells you that the Messenger of Allah (ﷺ) urinated standing up, do not believe him, for he would not urinate except while squatting."
Reference : Sunan an-Nasa'i 29In-book reference : Book 1, Hadith 29English translation : Vol. 1, Book 1, Hadith 29