Sa'id bin Jubayr said: Utbah bin Farqad wrote to Sayyiduna Abdullah bin al-Zubayr (may Allah be pleased with him) seeking his ruling about (the inheritance of) the grandfather, and he wrote in reply that the Messenger of Allah (peace and blessings be upon him) said: "If I were to take anyone from my Ummah besides my Lord as an intimate friend, I would have taken Abu Bakr as an intimate friend; but he is my brother in the religion and my companion in the cave." And indeed Abu Bakr (may Allah be pleased with him) used to place him (the grandfather) in the rank of the father.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13888