The prayer was called to begin, so he took a man by the hand and brought him forward to lead, since this man was the imam of his people. He said, "I heard the Messenger of Allah ﷺ say, 'When the prayer is called and one of you needs to relieve himself, let him begin with relieving himself.'"
حدثنا هناد بن السري حدثنا أبو معاوية عن هشام بن عروة عن أبيه
أقيمت الصلاة فأخذ بيد رجل فقدمه وكان إمام قومه وقال سمعت رسول الله ﷺ يقول إذا أقيمت الصلاة ووجد أحدكم الخلاء فليبدأ بالخلاء
No references are available.
Sourcing, sahih. Abu Dawud narrated it in the Book of Purification, chapter "Should a man pray while holding in his urine?" (no. 88), and Ibn Majah (no. 616), and others besides them, from the hadith of Hisham with this wording. Ibn Khuzayma graded it sahih (no. 932, 1652), as did Ibn Hibban (no. 194), Hakim (1/168), Dhahabi, and others.On this subject there are also narrations from Ayesha [Muslim, no. 67/560], Abu Hurairah [Abu Dawud, no. 91], Thawban [Abu Dawud, no. 90], and Abu Umama [Ibn Majah, no. 617].