Musnad Ahmad 962:169

Hashim ibn al-Qasim narrated to us, Bakr ibn Khunays narrated to us, from Layth ibn Abi Sulaym, from Zayd ibn Arta’ah, from Abu Umamah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Permission has not been granted to a servant for anything better than two rak'ahs that he performs. Indeed, righteousness is poured over the head of the servant as long as he is in his prayer. And the servants have not drawn closer to Allah with anything like that which has come forth from Him," meaning the Qur'an.