ذِكْرُ الْأَمْرِ بِضَمِّ الْفَخِذَيْنِ عِنْدَ السُّجُودِ لِلْمُصَلِّي
when one of you prostrates himself, he should not stretch out his forearms( on the ground) like a dog and he should join both of his thighs. (Using translation from Abū Dāʾūd 901)
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ «إِذَا سَجَدَ أَحَدُكُمْ فَلَا يَفْتَرِشِ افْتِرَاشَ الْكَلْبِ وَلْيَضُمَّ فَخِذَيْهِ»