Prevent the infection of sins when serve people

Numbers 19:1-22
The water of cleansing: red heifer without defact and has never under a yoke. Eleazar the priest; take some of its blood on his finger and sprinkle it 7 times toward the front of the Tent of Meeting. The heifer is to be burned, ashes of the heifer shall be kept by the Israelite community for use in the water of cleansing.
Anyone processed this ashes of heifer will be unclean till evening. He muse wash his clothes.
Anyone touched the dead body will be unclean 7 days, he must purify himself by the cleasing water on 3rd day and 7th day. He must wash his clothes and bathe with water.
The man who sprinkles or touches the water of cleansing will be unclean till evening, he must wash his clothes.
The ritual with the red heifer is the remedy for defilement by contact with a dead body. To minimize the risk of accidental defilement, tombs were later painted white.
Why?
Anyone who sprinkle the cleansing water will be unclean till evening, erase other's sin, might has some sin upon his body, so he is unclean till evening. It remind us that help others or serve others as a minister in church, the sin of the world easily affects the servant of the Lord. So we have to clean our heart and body, clothes before we serve it and after the service we must clean ourself through Jesus Christ.
Clean people can come to the Lord, but unclean people, has sin in him, could not come to the Lord. Jesus Christ is our savior, our redeemer. His blood may atones us no matter what I am when I turn to Him.
How?
The sin will infect to others, so be careful to serve the people with pure heart and the blessing of the Lord, let us not be attack from the evil.
The armor of God: be strong in the Lord and in his mighty power. Stand firm with the belt of truth buckled around your waist, with the breastpate of righteousness in place, and with your feet fitted with the readiness that comes from the gospel of peace. In addition to all this, take up the shield of faith, take the helmet of salvation and the sword of the Spirit.  Keep on praying for all the saints. (Ephesians 6:13-18)