Abu Uthmaan said:
I was with Salmaan (ra) under a tree and he took a dry branch and began to shake it until its leaves fell to the ground.
He said: O Abu Uthmaan! Will you not ask me why I am doing this?
I said: Why are you doing this?
He said: The Messenger (sallallahu alaihi wasallam) did the same to me while I was with him under a tree. He took a dry branch and began to shake it until all the leaves fell to the ground.
Then he said: O Salmaan! Will you not ask me why I am doing this? So I said: And why are you doing this? & he replied : “Indeed (each time) the Muslim performs wudhoo and beautifies it, then performs the five prayers his sins fall from him just like these leaves have fallen”
and then he (peace & blessing may be upon him recited the verse:
Establish the prayer at the two ends of the day and at the approaches of the night. Indeed the good deeds remove the evil deeds. This is the reminder for those who remember. (Surah Hud 11:114)