Musannaf Ibn Abi Shayba 3:2252

Waki’ narrated to us, from Ibn ‘Awn, from Ibn Sirin, who said: They mentioned the prostration of the Qur’an in the presence of ‘Aisha. She said: It is an obligatory act that I performed, or a voluntary act that I performed voluntarily. There is no Muslim who prostrates a prostration to Allah, except that Allah raises his degree by it and removes his sin from him.