It is narrated from Sayyiduna Fadalah bin Ubayd (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Do not ask about three people: a man who contends with Allah over His grandeur, for grandeur is His cloak and might is His lower garment; a man who doubts concerning the command of Allah; and the one who despairs of Allah's mercy."
Hadith Referenceالمعجم الكبير للطبراني / باب الفاء / 15880