Musannaf Ibn Abi Shayba 3:5975

Jarir ibn Abd al-Hamid narrated to us, from Mansur, from Salim ibn Abi al-Ja'd, who said: A man came to Abu Dharr in al-Rabadhah and said, "Where is Abu Dharr?" They said, "He is at the foot of that mountain with his sheep." He said: So I came to him, and he was praying. He was shortening the standing and lengthening the bowing and prostration. He said: When he finished praying, I said, "O Abu Dharr, I saw you praying, shortening the standing and lengthening the bowing and prostration." He said: "I was told that there is no Muslim who prostrates a prostration to Allah, except that Allah raises him a degree by it and erases a sin from him by it."