Muwatta Malik · Hadith 456
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ رَجُلٍ، مِنَ الأَنْصَارِ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم نَهَى أَنْ تُسْتَقْبَلَ الْقِبْلَةُ لِغَائِطٍ أَوْ بَوْلٍ .
Yahya related to me from Malik from one of the Ansar that the Messenger of Allah, may Allah bless him and grant him peace, forbade defecating or urinating while facing the qibla
Sahih Lighairihi · Salim al-Hilali