ʿAli ؓ said: I used to come to the Prophet ﷺ and ask permission to enter. If he was praying, he would say Subhan Allah, and if he was not praying, he would give me permission to enter.
عَلِيٌّ كُنْتُ آتِي النَّبِيَّ ﷺ فَأَسْتَأْذِنُ فَإِنْ كَانَ فِي صَلاةٍ سَبَّحَ وَإِنْ كَانَ فِي غَيْرِ صَلاةٍ أَذِنَ لِي