Ali bin Abi Talib (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) "forbade me from reciting while in the state of bowing (ruku'), and also forbade wearing gold and saffron-dyed (yellow) clothing."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6107