Hebrews 7:18-21 J.B. Phillips New Testament (PHILLIPS)
18-19 Quite plainly, then, there is a definite cancellation of the previous commandment because of its ineffectiveness and uselessness—the Law was incapable of bringing anyone to real maturity—followed by the introduction of a better hope, through which we approach our God.
The high Priesthood of Christ rests upon the oath of God
20-21 This means a “better” hope for us because Jesus has become our priest by the oath of God. Other men have been priests without any sworn guarantee, but Jesus has the oath of him that said of him: ‘The Lord has sworn and will not relent, You are a priest forever according to the order of Melchizedek’.