أُقِيمَتِ الصَّلاَةُ فَأَقْبَلَ عَلَيْنَا رَسُولُ اللَّهِ صلى الله عليه وسلم بِوَجْهِهِ فَقَالَ " أَقِيمُوا صُفُوفَكُمْ وَتَرَاصُّوا، فَإِنِّي أَرَاكُمْ مِنْ وَرَاءِ ظَهْرِي ".
Anas ibn Malik reported: The iqamah was called, and the Messenger of Allah ﷺ turned his face towards us and said, “Straighten your rows and close up the gaps, for I see you from behind my back.”
also in Sahih al-Bukhari 718, Sahih al-Bukhari 725