It is narrated from Rabah bin Abdur Rahman, who says: My grandmother narrated to me from her father (Sayyiduna Saeed bin Zaid, may Allah be pleased with him) that the Messenger of Allah, peace and blessings be upon him, said: The prayer of the one who does not have ablution is not accepted, and the ablution of the one who does not mention Allah (i.e., does not recite Bismillah) is not accepted. And whoever does not believe in me (Muhammad, peace and blessings be upon him), will not be able to believe in Allah Almighty. And the servant who does not love the Ansar, will not be able to believe in me.
Hadith Referenceالفتح الربانی / كتاب الفضائل والمناقب / 11548