(Imām Bukhārī narrates): Abū Ma'mar narrated to us, he said: 'Abdul-Wārith narrated to us, from 'Abdul-'Azīz, from Anas, may Allāh be pleased with him, that the Prophet ﷺ said:
Keep the rows straight, and stand close together, for indeed I see you even from behind my back.
حَدَّثَنَا أَبُو مَعْمَرٍ، قَالَ حَدَّثَنَا عَبْدُ الوَارِثِ، عَنْ عَبْدِ العَزِيزِ بْنِ صُهَيْبٍ، عَنْ أَنَسِ بْنِ مَالِكٍ: أَنَّ النَّبِيَّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ قَالَ: «أَقِيمُوا الصُّفُوفَ، فَإِنِّي أَرَاكُمْ خَلْفَ ظَهْرِي»
Reference: Sahih Al Bukhari 718