It is narrated from Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "I have been forbidden from reciting the Qur'an while in the state of bowing and prostration. Therefore, glorify the greatness of your Lord in bowing, and strive and seek in supplication during prostration. For it is more likely that (your supplication) will be accepted."
Hadith Referenceمسند الإمام الشافعي / كتاب الصلاة / 224
Hadith Takhrijاخرجه مسلم الصلاة، باب النهي عن قرأة القرآن في الركوع والسجود: 479