Musannaf Ibn Abi Shayba 3:2251

Abu al-Ahwas narrated to us, from Abu Ishaq, from Makhariq, who said: I passed by Abu Dharr in al-Rabadhah while I was a pilgrim, so I entered his house and saw him praying. He would lighten the standing [duration] to the extent of reciting "Indeed, We have granted you, [O Muhammad], the al-Kawthar" and "When the victory of Allah has come and the conquest," and he would increase the bowing and prostrating. When he finished his prayer, I said: "O Abu Dharr, I saw you lightening the standing and increasing the bowing and prostrating." He said: "I heard the Messenger of Allah, may Allah bless him and grant him peace, say: 'There is no servant who prostrates a prostration to Allah, or bows a bowing for Him, except that Allah removes a sin from him by it and raises a degree for him by it.'"