Qays bin Abi Hazim narrates from Sayyiduna Bilal (may Allah be pleased with him) that he saw a man praying badly, completing neither its bowing nor its prostration. So he said: "If you were to die right now, you would die upon a religion other than that of Isa (peace be upon him)."
Hadith Referenceالمعجم الكبير للطبراني / باب الباء / 1081