Numbers 19:13 Whosoever toucheth the dead body of any man that is dead, and purifieth not himself, defileth the tabernacle of the Lord; and that soul shall be cut off from Israel: because the water of separation was not sprinkled upon him, he shall be unclean; his uncleanness is yet upon him.
Ezekiel 36:25 Then will I sprinkle clean water upon you, and ye shall be clean: from all your filthiness, and from all your idols, will I cleanse you.
Blood, water or oil is often sprinkled in the Old Testament, and the text sometimes clearly indicates that sprinkling is performed to clean or purify. Individuals are purified by sprinkling. Anyone who touches a dead body is unclean and cannot enter the tabernacle unless they have been sprinkled with the ashes of the red heifer. We must separate ourselves from dead flesh or we cannot enter Heaven (tabernacle). Otherwise, we must be sprinkled to enter Heaven (tabernacle).
Isaiah 52:15 So shall he sprinkle many nations; the kings shall shut their mouths at him: for that which had not been told them shall they see; and that which they had not heard shall they consider.
The nations will be sprinkled, and the context of this verse indicates that this will occur at the time of the end. This does not mean all people will be made clean. The nations will not be sprinkled upon, the nations will be what is sprinkled.
Matthew 25:32 And before him shall be gathered all nations: and he shall separate them one from another, as a shepherd divideth his sheep from the goats: And he shall set the sheep on his right hand, but the goats on the left. Then shall the King say unto them on his right hand, Come, ye blessed of my Father, inherit the kingdom prepared for you from the foundation of the world:
In the New Testament we learn that the nations will be separated. To sprinkle is to separate, and this separating clearly seems to occur at the end times.
The nations are separated into two categories, sheep and goats. The sheep are welcomed into Heaven, but the goats are not. The nations are separated into those who make it to Heaven, and those who do not make it to Heaven.
It could be said that Christians are the sheep, and everyone else are goats. Perhaps people who live up to the Law are the sheep. Perhaps all good people are sheep, and all bad people are goats. It seems unlikely that there would be such a big mystery, and such a very common ceremony like sprinkling, if all it symbolizes is separating those who make it to Heaven from those who do not make it to Heaven.
In the Old Testament individuals are purified by sprinkling. If Christians are separated from heathen, that act of separation does not make them pure. If good people are separated from bad people, the act of separation is not what makes them good.
If the flesh is separated from the spirit, the very act of separating makes the child of God pure.
In the end, God sprinkles the nations, and this is how God destroys evil, and this is how God makes pure all His children.