Hadith 381
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ زَيْدِ بْنِ أَسْلَمَ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، قَالَ لاَ يُصَلِّيَنَّ أَحَدُكُمْ وَهُوَ ضَامٌّ بَيْنَ وَرِكَيْهِ .
Yahya related to me from Malik from Zayd ibn Aslam that Umar ibn al-Khattab said, "You should not pray while you are holding your bowels
Mauquf Daif (Salim al-Hilali)
Muwatta Malik 381 · Book 9, Hadith 56