Numbers 19:3
And ye shall give her unto Eleazar the priest, that he may bring her forth without the camp, and one shall slay her before his face: And ye shall give her unto Eleazar the priest, that he may bring her forth without the camp, and one shall slay her before his face:
The red heifer was to be led forth outside the camp and slain there. It was entrusted to Eleazar the priest and slain before his face as a sacrifice for the congregation's purification from ceremonial defilement. Contact with death in this rite represented the pollution of sin, because death came as a consequence of sin. The heifer itself represents Christ, the one great offering whose sacrifice redeems from sin.
Its slaying outside the camp prefigures Christ suffering outside Jerusalem, at Calvary outside the city's gates. This shows His death was for all mankind and not for the Hebrews alone, offering redemption and salvation to the fallen world.