Sunan Abi Dawud 21401
In-book no 897حَدَّثَنَا مُسْلِمُ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا شُعْبَةُ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ " اعْتَدِلُوا فِي السُّجُودِ وَلاَ يَفْتَرِشْ أَحَدُكُمْ ذِرَاعَيْهِ افْتِرَاشَ الْكَلْبِ " .
Anas reported the Messenger of Allah(ﷺ) as saying; Adopt a moderate position when prostrating yourselves, and see that none of you stretches out his forearms(on the ground) like a dog.