Musnad Ahmad 28:40

Yahya narrated to us, from Ibn Jurayj, from Ibn Abi Mulaykah, from Yahya ibn Hakim ibn Safwan, from Abdullah ibn Amr ibn al-Aas, who said: I collected the Quran and recited it every night. That reached the Messenger of Allah, peace and blessings of Allah be upon him, and he said: "I fear that a time may become long for you, and you will become weary. Recite it every month." I said: "O Messenger of Allah, let me enjoy my strength and my youth." He said: "Recite it every twenty [days]." I said: "O Messenger of Allah, let me enjoy my strength and my youth." He said: "Recite it in ten [days]." I said: "O Messenger of Allah, let me enjoy my strength and my youth." He said: "Recite it every seven [days]." I said: "O Messenger of Allah, let me enjoy my strength and my youth." But he refused.