Al-Adab Al-Mufrad, Hadith 807 ⓘ
Anas said, "I used to serve the Prophet, may Allah bless him and grant him peace." He continued, "I used to enter without asking for permission to enter. One day I came and he said, 'My son, there is a new situation. You should not come in unless you have permission.'"
حَدَّثَنَا مُحَمَّدٌ، قَالَ: حَدَّثَنَا عَبْدُ اللهِ، قَالَ: أَخْبَرَنَا جَرِيرُ بْنُ حَازِمٍ، عَنْ سَلْمٍ الْعَلَوِيِّ قَالَ: سَمِعْتُ أَنَسًا يَقُولُ: كُنْتُ خَادِمًا لِلنَّبِيِّ صلى الله عليه وسلم، قَالَ: فَكُنْتُ أَدْخُلُ بِغَيْرِ اسْتِئْذَانٍ، فَجِئْتُ يَوْمًا، فَقَالَ: كَمَا أَنْتَ يَا بُنَيَّ، فَإِنَّهُ قَدْ حَدَثَ بَعْدَكَ أَمْرٌ: لا تَدْخُلَنَّ إِلا بِإِذْنٍ.
also referenced under: Book 33, Hadith 54 (In-Book) & Book 33, Hadith 807 (English)