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 ibnal-Khattab said, "You should not pray while you are holding yourbowels." Translation Not Available

Book Ref: Muwatta Imam Malik Book 9 Hadith 384
Web Ref:  Muwatta Imam Malik Book 9 Hadith 53