Hebrews 7:6

6 As for Melchizedek, he was not a descendant of Levi. But he still received a tenth part of what Abraham had. He also asked God to bless Abraham. But Abraham was the one who had already received God's promises.

7:5The Israelites were descendants of Jacob, who was Abraham's grandson. God gave Jacob a new name, Israel. Jacob's 12 sons became the ancestors of Israel's 12 tribes. Levi was the ancestor of the tribe of Levi. Levites who were descendants of Aaron were priests who served God in the temple. The other Levites helped the priests. See Numbers 1:50; Exodus 28:1.