(493) بَابُ الاسْتِئْذَانُ غَيْرُ السَّلامِ
Abu Hurayra said, "When someone comes in and does not say, 'Peacebe upon you,' then say, 'No,' until he brings the key which is the greeting(salam)."
Reference: Al-Adab Al-Mufrad 1067
In-book reference: Book 43, Hadith 17
English translation: Book 43, Hadith 1067