A man of Banu Amir told that he asked the Prophet ﷺ for permission (to enter the house) when he was in the house, saying: May I enter ? The Prophet ﷺ said to his servant: Go out to this (man) and teach him how to ask permission to enter the house, and say to him: "Say : Peace be upon you. May I enter?" The man heard it and said: Peace be upon you! May I enter ? The Prophet ﷺ permitted him and he entered.  

أَنَّهُ اسْتَأْذَنَ عَلَى النَّبِيِّ ﷺ وَهُوَ فِي بَيْتٍ فَقَالَ أَلِجُ فَقَالَ النَّبِيُّ ﷺ لِخَادِمِهِ اخْرُجْ إِلَى هَذَا فَعَلِّمْهُ الاِسْتِئْذَانَ فَقُلْ لَهُ قُلِ السَّلاَمُ عَلَيْكُمْ أَأَدْخُلُ فَسَمِعَهُ الرَّجُلُ فَقَالَ السَّلاَمُ عَلَيْكُمْ أَأَدْخُلُ فَأَذِنَ لَهُ النَّبِيُّ ﷺ فَدَخَلَ