I used to serve the Messenger of Allah ﷺ, and I would enter upon him without seeking permission. One day I came and entered upon him, and he said, "My son, a new command has come, so do not enter upon me except with permission."
كنت أخدم رسول الله ﷺ فكنت أدخل عليه بغير إذن، فجئت ذات يوم، فدخلت عليه، فقال: يا بني إنه قد حدث أمر، فلا تدخل علي إلا بإذن.
Ahmad (13176), Abu Yaala (4276), and Bukhari in Adab al-Mufrad (807) all narrated it through the route of Salm Alawi, who said, "I heard Anas bin Malik," and then mentioned it.Its chain is hasan because of Salm Alawi, who is disputed and has few narrations, but nothing in his hadith is objectionable, and Ibn Main deemed him reliable in one report.