Sa'id ibn al-Musayyib سعيد بن المسيب بن حزن أبو محمد القرشي · The Book of Forgetfulness (In Prayer)

"I knocked at the door when the Messenger of Allah (ﷺ) was offering a voluntary prayer. The door was in the direction of the Qiblah so he took a few steps to his right or left and opened the door, then he went back to where he was praying."