Jami` at-Tirmidhi 276
جامع الترمذي#276Sahihحَدَّثَنَا مَحْمُودُ بْنُ غَيْلاَنَ، حَدَّثَنَا أَبُو دَاوُدَ، أَخْبَرَنَا شُعْبَةُ، عَنْ قَتَادَةَ، قَالَ سَمِعْتُ أَنَسًا، يَقُولُ إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " اعْتَدِلُوا فِي السُّجُودِ وَلاَ يَبْسُطَنَّ أَحَدُكُمْ ذِرَاعَيْهِ فِي الصَّلاَةِ بَسْطَ الْكَلْبِ " . قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ .
Anas narrated that :Allah's Messenger said: "Be balanced in the prostration, and let one of you not spread his forearms (on the ground) in the Salat like the spreading of the dog
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
In-book reference: 2:128