It was narrated that Anas said:
"The Messenger of Allah ﷺturned to face us when he stood up to pray, before he said the Takbir and said: 'Make your rows straight and come close to one another, for I can see you behind my back."'
أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، أَنْبَأَنَا إِسْمَاعِيلُ، عَنْ حُمَيْدٍ، عَنْ أَنَسٍ، - رضى الله عنه - قَالَ أَقْبَلَ عَلَيْنَا رَسُولُ اللَّهِ صلى الله عليه وسلم بِوَجْهِهِ حِينَ قَامَ إِلَى الصَّلاَةِ قَبْلَ أَنْ يُكَبِّرَ فَقَالَ " أَقِيمُوا صُفُوفَكُمْ وَتَرَاصُّوا فَإِنِّي أَرَاكُمْ مِنْ وَرَاءِ ظَهْرِي " .
• Sunan an-Nasa'i, 814
• Sunan an-Nasa'i, Vol. 1, Book of Leading the Prayer (Al-Imamah), Hadith 815
• Sunan an-Nasa'i, Book of Leading the Prayer (Al-Imamah), Hadith 815