حَدَّثَنَا عَلِيُّ بْنُ إِسْحَاقَ أَنْبَأَنَا عَبْدُ اللَّهِ أَنْبَأَنَا يَحْيَى بْنُ أَيُّوبَ عَنْ عُبَيْدِ اللَّهِ بْنِ زَحْرٍ عَنْ عَلِيِّ بْنِ يَزِيدَ عَنِ الْقَاسِمِ عَنْ أَبِي أُمَامَةَ أَنَّ عَلِيَّ بْنَ أَبِي طَالِبٍ رَضِيَ اللَّهُ عَنْهُ أَخْبَرَهُ أَنَّهُ كَانَ يَأْتِي النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ فَكُنْتُ إِذَا وَجَدْتُهُ يُصَلِّي سَبَّحَ فَدَخَلْتُ وَإِذَا لَمْ يَكُنْ يُصَلِّي أَذِنَ
مسند امام احمد بن حنبل · Hadith 899
It was narrated from Abu Umamah that 'Ali bin Abi Talib (RA) told him that he used to go to the Prophet (PBUH). He said: If I found him praying, he would say tasbceh and I would enter, and if he was not praying, he would give me permission to enter.
Translated by Dr. Muhammad Muhsin Khan · Reviewed by Islamic University of Madinah · Published March 2020