He has become a high priest forever, in the order of Melchizedek

 Hebrews 6:1-20

To their loss they are crucifying the Son of God all over again and subjecting him to public disgrace. Land that drinks in the rain often falling on it and that produces a crop useful to those for whom it is farmed receives the blessing of God. But land that produces thorns and thistles is worthless and is in danger of being cursed. In the end it will be burned.

God is not unjust; he will not forget your work and the love you have shown him as you have helped his people and continue to help them. We want each of you to show this same diligence to the very end, so that what you hope for may be fully realized. We do not want you to become lazy, but to imitate those who through faith and patience inherit what has been promised.

When God made his promise to Abraham, since there was no one greater for him to swear by, he swore by himself, saying, “I will surely bless you and give you many descendants.” And so after waiting patiently, Abraham received what was promised.

God did this so that, by two unchangeable things in which it is impossible for God to lie, we who have fled to take hold of the hope set before us may be greatly encouraged. We have this hope as an anchor for the soul, firm and secure. It enters the inner sanctuary behind the curtain, where our forerunner, Jesus, has entered on our behalf. He has become a high priest forever, in the order of Melchizedek.

Why?

In the order of Melchizedek is the promise of the Lord, the Lord is the great God, we can not say anything but go forward with faith, love, and hope through Jesus Christ.

Abraham has faith in the Lord, and God's word came true, so we can follow the way of Jesus Christ and many apostles.

Paul reminds us not to go back to the beginning step of faith. If it does, it's worse than the beginning. 

How?

Keep forward with faith, love, and hope to live out every day on earth until we meet our Lord