Ibn Umar reported: The Messenger of Allah, peace and blessings be upon him, said, “Verily, when a servant stands to pray, his sins are placed on top of his head and shoulders. Every time he bows or prostrates, they fall away from him.”
Source: Ṣaḥīḥ Ibn Ḥibbān 1734
SubhanAllah, I just learnt something beautiful…
Whilst we are in qiyaam all of our sins are placed on our head and shoulders, as we fall into ruku, all those sins start to fall off of us, which means… when we fall into sujood, the closest position to Allah (SWT), we are pure.