Abu Ishaq narrated that Sayyiduna Qutham bin al-Abbas (may Allah be pleased with them both) was asked: "How did Ali (may Allah be pleased with him) inherit from the Messenger of Allah (peace and blessings be upon him) rather than all of you?" He said: "Indeed, he was the first to join him (peace and blessings be upon him) and the one who stayed closest to him (peace and blessings be upon him)."
Hadith Referenceالمعجم الكبير للطبراني / باب القاف / 16136