Death is ugly and strange. It is not at all a natural part of life like the unbelieving world wants everyone to accept. It is a violent separation of material and immaterial that was brought into the world as a curse for disobedience, and it is an ever-present reminder of the foulness of that transgression of God's command. The Old Covenant Israelites had some interesting practices when it came to dead folks. They weren't really supposed to touch them. If an Israelite did touch a dead body, he was ceremonially unclean for seven days (Numbers 19:11). That means that he couldn't take part in any of the feasts, sacrifices, or special rituals at the tabernacle or temple. For this reason, those who had more responsibilities in the cultic worship - like the Levites and priests - had to live by even stricter commands involving the touching of dead bodies (Leviticus 21:1-4).
This foulness of death was considered so potent that even if you just happened to be in the same tent with someone when he or she died, you were to be unclean for seven days (Numbers 19:14). And not only that, but any uncovered container was considered unclean as well (verse 15), which meant breaking them if they were earthenware, or scrubbing them if they were brass, and all food or drink inside had to be thrown away (Leviticus 11:33-34).
At this point we have to ask, "What's the big deal?" Why would I have to pour my coffee out and break the mug if I just happened to be sitting by someone's bedside when he died? Why would I have to wash myself with water mixed with ashes from a burnt red heifer (Numbers 19:1-13)? It's not because they believed that the body released pathogens at the moment of death or anything like that. It's simply because death is the punishment for sin (Genesis 2:17, Romans 6:23). And every time an Israelite came into contact with this constant reminder of God's wrath, the encounter would start a seven-day reflection on the difference between God's holiness and man's sinfulness.
What is significant about all of this for New Covenant Christians is how closely related all of these Old Testament cleansing rites are to the baptism of the New Testament. Ezekiel 36:25-27, in speaking of the New Covenant promises to God's people, uses the imagery of purification from uncleanness to illustrate the new birth: "I will sprinkle clean water on you , and you shall be clean from all your uncleannesses...And I will give you a new heart, and I new spirit I will put within you." This is the very thing that is pictured in Christian baptism.
How can we who died to sin still live in it? Do you not know that all of us who have been baptized into Christ Jesus were baptized into His death? We were buried therefore with Him by baptism into death, in order that, just as Christ was raised from the dead by the glory of the Father, we too might walk in newness of life (Romans 6:2-4)
Those who came into contact with the evidence of God's judgment were to wash with "living" water (the actual Hebrew wording of Numbers 19:17) mixed with the ashes of a sacrifice made outside the camp in order to be cleansed from the taint of death. Likewise, we who have placed our faith in Christ are to be baptized in order to show our identity with His death which was carried out for us outside the camp (Hebrews 13:12). But in baptism, the sacrifice is also mingled with "living water" (John 4:14), for we are raised from it in newness of life. In this one act, we show that Christ has cleansed us from the ultimate effects of the curse, for we will one day rise just as He did. When we plunge someone into the waters of baptism, we are proclaiming to the world that Christ has washed the death off of that person and now the person is clean in God's eyes and able to come into His presence for worship.