Sunan Abi Dawud
Sunan Abi Dawud 5027
Arabic hadith text
حَدَّثَنَا ابْنُ الْعَلاَءِ، عَنْ وَكِيعٍ، عَنْ سُفْيَانَ، عَنْ سُهَيْلٍ، نَحْوَهُ قَالَ " فِي الصَّلاَةِ فَلْيَكْظِمْ مَا اسْتَطَاعَ " .
Translation
A similar report from Suhayl says: During prayer, restrain the yawn as much as possible.