Sunan an Nasai
814
Sahih+2

It was narrated that Anas said:"The Messenger of Allah (ﷺ)turned 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

SahihAbu Ghuddah
SahihAl-Albani