Abu Uthman reported,

We were with Salman under a tree when he took one of its branches and shook it, causing its leaves to fall. He then said, "Will you not ask me why I did that?"We said, "Tell us."He said, "We were with the Messenger of Allah ﷺ in the shade of a tree when he took one of its branches and shook it, causing its leaves to fall. He then said, 'Will you not ask me why I did that?'We said, 'Tell us, Messenger of Allah.'He said, 'When the Muslim servant stands for prayer, his sins fall away from him just as the leaves of this tree fall.'"

حدثنا يزيد أخبرنا حماد بن سلمة عن علي بن زيد

عن أبي عثمان النهدي قال

كنا مع سلمان تحت شجرة فأخذ غصنا منها فنفضه فتساقط ورقه فقال ألا تسألوني عما صنعت فقلنا أخبرنا فقال كنا مع رسول الله ﷺ في ظل شجرة فأخذ غصنا منها فنفضه فتساقط ورقه فقال ألا تسألوني عما صنعت فقلنا أخبرنا يا رسول الله فقال إن العبد المسلم إذا قام إلى الصلاة تحاتت عنه خطاياه كما تحات ورق هذه الشجرة