'Sons of Levi' in the Bible

And these are the names of the sons of Levi according to their generations; Gershon, and Kohath, and Merari: and the years of the life of Levi were an hundred thirty and seven years.

Then Moses stood in the gate of the camp, and said, Who is on the LORD'S side? let him come unto me. And all the sons of Levi gathered themselves together unto him.

And the sons of Levi did according to the word of Moses: and there fell of the people that day about three thousand men.