Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
abudawud:5179ʿUbaydullāh b. Muʿādh from my father > Shuʿbah > Manṣūr > Ribʿī > a man from Banī ʿĀmir

I heard it and so I said: Peace be upon you. May I enter?  

أبو داود:٥١٧٩حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُعَاذٍ حَدَّثَنَا أَبِي حَدَّثَنَا شُعْبَةُ عَنْ مَنْصُورٍ عَنْ رِبْعِيٍّ عَنْ رَجُلٍ مِنْ بَنِي عَامِرٍ

أَنَّهُ اسْتَأْذَنَ عَلَى النَّبِيِّ ﷺ بِمَعْنَاهُ قَالَ فَسَمِعْتُهُ فَقُلْتُ السَّلاَمُ عَلَيْكُمْ أَأَدْخُلُ