Imam Tirmizi narrated in his “Sunnan”:

4033 – حَدَّثَنَا يُوسُفُ بْنُ مُوسَى الْقَطَّانُ الْبَغْدَادِيُّ، حَدَّثَنَا مَالِكُ بْنُ إِسْمَاعِيلَ، عَنْ مَنْصُورِ بْنِ أَبِي الأَسْوَدِ، حَدَّثَنِي كَثِيرٌ أَبُو إِسْمَاعِيلَ، عَنْ جُمَيْعِ بْنِ عُمَيْرٍ التَّيْمِيِّ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ لأَبِي بَكْرٍ ‏”‏ أَنْتَ صَاحِبِي عَلَى الْحَوْضِ وَصَاحِبِي فِي الْغَارِ ‏”‏ ‏.‏ قَالَ هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ غَرِيبٌ ‏.‏

From ibn Umar:  Messenger of Allah (sallalahu alaihi wa sallam) said to Abu Bakr: You are my companion on the pool, and companion in the cave”.

Imam Tirmizi said it is hasan -saheeh – gharib. Shaykhana Albani said report is weak in “Daeef at-Tirmizi”.

In the chain of this hadith Jami ibn Umayr at-Taymi, Abul Aswad.  He was accused in lie by ibn Hibban and ibn Numayr and weakened by Bukhari and ibn Adi. (See Tazhib at-Tahzib 1/315). Ibn Hibban said that he was rafidi which use to fabricate ahadeth.