Musnad Ahmad 1153:202

Isma'il narrated to us, he said: Hisham informed us, from Qatadah, from Zurarah ibn Awfa, from Sa'd ibn Hisham, from 'Aishah, she said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "The one who recites the Qur'an while he is proficient in it is with the noble, righteous scribes. And the one who recites it while it is difficult for him has two rewards."