Musnad Ahmad 1153:617

Bahz narrated to us, he said: Hammam narrated to us, Qatadah narrated to us, from Zurarah ibn Awfa, from Sa'd ibn Hisham, from Aisha, that the Prophet, peace and blessings of Allah be upon him, said: "Indeed, the one who recites the Quran and is skilled in it is with the noble, righteous messenger-angels. And the one who recites it while it is difficult for him, his recitation is strenuous, he has two rewards."