It is narrated from Sayyiduna Abu al-Hamra' (may Allah be pleased with him), the servant of the Prophet (peace and blessings be upon him); he said: I heard the Messenger of Allah (peace and blessings be upon him) say: "When I was taken on the Night Journey (Mi'raj) and I entered Paradise, I saw written on the leg of the Throne: La ilaha illallah, Muhammad Rasulullah (There is no god but Allah, Muhammad is the Messenger of Allah); I supported him with Ali and helped him."
Hadith Referenceالمعجم الكبير للطبراني / باب الهاء / 18746