عَنِ ابْنِ عَبَّاسٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «أُمِرْتُ أَنْ أَسْجُدَ عَلَى سَبْعَةِ أَعْظُمٍ عَلَى الْجَبْهَةِ وَالْيَدَيْنِ وَالرُّكْبَتَيْنِ وَأَطْرَافِ الْقَدَمَيْنِ وَلَا نَكْفِتَ الثِّيَاب وَلَا الشّعْر»

Anas reported God’s Messenger 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.” (Bukhari and Muslim.)