'Set apart' in the Bible

These are the names of the sons of Aaron, the priests who were anointed, whom he set apart to minister as priests.

Because all the first-born are Mine. On the day that I struck all the first-born in the land of Egypt I set apart to Myself all the first-born in Israel, both man and animal. They shall be Mine. I am Jehovah.

And he shall set apart to Jehovah the days of his separation, and shall bring a lamb of the first year for a guilt offering. But the former days shall be lost, because his separation was defiled.