Mishkat al-Masabih 30 Fine Qualities كتاب المناقب 53

وَعَنْ عَائِشَةَ أَنَّ أَبَا بَكْرٍ دَخَلَ عَلَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَقَالَ: «أَنْت عتيقُ اللَّهِ من النَّار» . فَيَوْمئِذٍ سمي عتيقا. رَوَاهُ التِّرْمِذِيّ

`A’isha told that Abu Bakr came in to visit God’s messenger who said, “You are God’s freedman ( atiq ) from hell,” so on that day he was named `Atiq. Tirmidhi transmitted it.