It is narrated from Sayyiduna Uqbah bin Amir (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) prayed wearing a silk farruj (a cloak slit at the back), then took it off. I said: O Messenger of Allah! You prayed wearing it, then you took it off? He (peace and blessings be upon him) said: "This is not the clothing of the God-fearing."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14830