Abdullah bin Qays, Abu Musa Ashari, greeted Umar bin Khattab, may Allah be pleased with them, with the salutation of peace three times, but was not granted permission to enter, so he turned back. Umar sent someone after him to ask why he had returned.He replied, "I heard the Messenger of Allah ﷺ say, 'When one of you gives the greeting of peace three times and receives no answer, let him return.'"
حدثنا عبد الرزاق أخبرنا معمر عن سعيد الجريري عن أبي نضرة
سلم عبد الله بن قيس أبو موسى الأشعري على عمر بن الخطاب رضي الله تعالى عنهم ثلاث مرات فلم يؤذن له فرجع فأرسل عمر في أثره لم رجعت قال إني سمعت رسول الله ﷺ يقول إذا سلم أحدكم ثلاثا فلم يجب فليرجع
Its isnad is sahih, its narrators being well-known and trustworthy. This hadith was previously narrated by Abu Saeed, recounting what Abu Musa and Umar did, in 11088.