Sunan Ibn Majah, Book 1, Hadith 662 (In-Book) ⓘ
It was narrated from Thawban that: The Messenger of Allah said: "No one among the Muslims should stand to pray when he is suppressing (the need to urinate or defecate), until he has to relieve himself."
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُصَفَّى الْحِمْصِيُّ، حَدَّثَنَا بَقِيَّةُ، عَنْ حَبِيبِ بْنِ صَالِحٍ، عَنْ أَبِي حَىٍّ الْمُؤَذِّنِ، عَنْ ثَوْبَانَ، عَنْ رَسُولِ اللَّهِ ـ صلى الله عليه وسلم ـ أَنَّهُ قَالَ " لاَ يَقُومُ أَحَدٌ مِنَ الْمُسْلِمِينَ وَهُوَ حَاقِنٌ حَتَّى يَتَخَفَّفَ " .
also referenced under: Hadith 619 (Reference) & Volume 1, Book 1, Hadith 619 (DarusSalam)