Sahih Muslim 493
Sahih Muslim · Book 4: The Book of Prayers · Moderation In Prostration; Placing The Hands On The Ground, Keeping The Elbows Up, Away From The Sides, And Lifting The Belly Up Off The Thighs When Prostrating
This hadith has been narrated by Shu'ba with the same chain of transmitters. And in the hidith transmitted by Ibn Ja'far (the words are):
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى ، وَابْنُ، بَشَّارٍ قَالاَ حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ ، ح قَالَ وَحَدَّثَنِيهِ يَحْيَى بْنُ حَبِيبٍ ، حَدَّثَنَا خَالِدٌ، - يَعْنِي ابْنَ الْحَارِثِ - قَالاَ حَدَّثَنَا شُعْبَةُ ، بِهَذَا الإِسْنَادِ وَفِي حَدِيثِ ابْنِ جَعْفَرٍ " وَلاَ يَتَبَسَّطْ أَحَدُكُمْ ذِرَاعَيْهِ انْبِسَاطَ الْكَلْبِ " .
" None of you should stretch out his forearms like the stretching out of a dog."