Mishkat al-Masabih 30 Fine Qualities كتاب المناقب 50

وَعَن ابْنِ عُمَرَ عَنْ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ لِأَبِي بَكْرٍ: «أَنْتَ صَاحِبِي فِي الْغَارِ وصاحبي على الْحَوْض» . رَوَاهُ التِّرْمِذِيّ

Ibn `Umar told that God’s messenger said to Abu Bakr, “You were my companion in the cave, and you will be my companion at the Pond. Tirmidhi transmitted it.