'Order of Melchizedek' in the Bible

As he says in another place, You are a priest for ever after the order of Melchizedek.

Being named by God a high priest of the order of Melchizedek.

Where Jesus has gone before us, as a high priest for ever after the order of Melchizedek.

Now if it was possible for things to be made complete through the priests of the house of Levi (for the law was given to the people in connection with them), what need was there for another priest who was of the order of Melchizedek and not of the order of Aaron?

For it has been witnessed of him, You are a priest for ever after the order of Melchizedek.