Musannaf Ibn Abi Shaybah

Hazrat Salim bin Abi Al-Ja'd says that a man came to Hazrat Abu Dharr and asked, "Where is Abu Dharr?" The people said that he is on the top of the mountain with his small herd. I went to him and found him praying. He would keep the standing (qiyam) short and prolong the bowing (ruku) and prostration (sujud). When he finished the prayer, I said, "O Abu Dharr! I saw that you kept the standing in prayer short and prolonged the bowing and prostration. What is the reason for this?" He replied, "The Messenger of Allah, peace and blessings be upon him, said that whenever a Muslim performs a prostration for the sake of Allah, Allah raises him one degree because of it and removes one sin from him."