Sahih al-Bukhari 822
Sahih al-Bukhari · Book 10: Call to Prayers (Adhaan) · One should not put the forearms on the ground during prostrations
Narrated Anas bin Malik:
حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ ، قَالَ حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ ، قَالَ حَدَّثَنَا شُعْبَةُ ، قَالَ سَمِعْتُ قَتَادَةَ ، عَنْ أَنَسِ بْنِ مَالِكٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " اعْتَدِلُوا فِي السُّجُودِ، وَلاَ يَبْسُطْ أَحَدُكُمْ ذِرَاعَيْهِ انْبِسَاطَ الْكَلْبِ " .
The Prophet (ﷺ) said, "Be straight in the prostrations and none of you should put his forearms on the ground (in the prostration) like a dog."