"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." (Using translation from Nasāʾī 1206)  

قَالَتِ «اسْتَفْتَحْتُ الْبَابَ وَرَسُولُ اللهِ ﷺ يُصَلِّي تَطَوُّعًا وَالْبَابُ عَلَى الْقِبْلَةِ فَمَشَى عَنْ يَمِينِهِ أَوْ عَنْ يَسَارِهِ فَفَتَحَ الْبَابَ ثُمَّ رَجَعَ إِلَى مُصَلَّاهُ»