Leviticus 11:25 New International Version (NIV)
25 Whoever picks up one of their carcasses must wash their clothes, and they will be unclean till evening.
In order to worship, people need to be prepared. There were things that made a person unclean for worship. This could be sin or it could have been disobedience, or just a natural act like childbirth or touching a dead body. This was not that God rejected the person, but worship was to be done decently and have order. God was teaching his people respect and regard for who he was and how he was to be treated. Today, we also need to be prepared for worship. We cannot live any way we want during the week, and then rush into God’s presence on Sunday. It is important to prepare ourselves by repenting from sin and correcting errors when then happen. Also, have thoughtful anticipation of what it means to be with other believers and worship. Be mindful of God all week, each and every day.