Musannaf Ibn Abi Shayba 22:148

Jarir narrated to us, from Mansur, from Abu al-Duha, who said: Al-Dahhak ibn Qays used to say: "O people, teach your children and your families the Quran, for whoever among the Muslims is written for him that Allah will enter him into Paradise, two angels will come to him and flank him, and they will say to him: 'Ascend in the degrees of Paradise,' until they settle him therein at the point where his knowledge of the Quran ends."