Muwatta Malik 380

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، أَنَّ عَبْدَ اللَّهِ بْنَ الأَرْقَمِ، كَانَ يَؤُمُّ أَصْحَابَهُ فَحَضَرَتِ الصَّلاَةُ يَوْمًا فَذَهَبَ لِحَاجَتِهِ ثُمَّ رَجَعَ فَقَالَ إِنِّي سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ ‏ "‏ إِذَا أَرَادَ أَحَدُكُمُ الْغَائِطَ فَلْيَبْدَأْ بِهِ قَبْلَ الصَّلاَةِ ‏"‏ ‏.‏

Yahya related to me from Malik from Hisham ibn Urwa from his father that Abdullah ibn al-Arqam used to lead his companions in prayer. The time for prayer came one day and he went to relieve himself. When he returned, he said, "I heard the Messenger of Allah, may Allah bless him and grant him peace, say, 'If you wish to defecate, you should do so before the prayer

Reference

Muwatta Malik 380

In-book

Book 9, Hadith 55