Hebrews 5

In his writings to the Jews, Paul taught basic doctrine concerning priesthood authority and its importance.  Speaking of the Savior -

"Though he were a Son, yet learned he obedience by the things which he suffered;
9 And being made perfect, he became the author of eternal salvation unto all them that obey him;
10 Called of God an high priest after the order of Melchisedec."  (New Testament | Hebrews 5:8 - 10)

Thus Jesus Christ received His priesthood office and authority from the Father.  For those that may not understand why Paul spoke of the order of Melchisedec, in modern day we learn -

"Why the first is called the Melchizedek Priesthood is because Melchizedek was such a great high priest.
3 Before his day it was called the Holy Priesthood, after the Order of the Son of God.
4 But out of respect or reverence to the name of the Supreme Being, to avoid the too frequent repetition of his name, they, the church, in ancient days, called that priesthood after Melchizedek, or the Melchizedek Priesthood."  (Doctrine and Covenants | Section 107:2 - 4)

Of those that hold this priesthood or have this priesthood authorityconferred upon them, Paul explained -

"FOR every high priest taken from among men is ordained for men in things pertaining to God, that he may offer both gifts and sacrifices for sins:
2 Who can have compassion on the ignorant, and on them that are out of the way..."  (New Testament | Hebrews 5:1 - 2)

Those that hold the Melchizedek priesthood administer the ordinances, covenants and blessings of the gospel for -

"....this greater priesthood administereth the gospel and holdeth the key of the mysteries of the kingdom, even the key of the knowledge of God.
20 Therefore, in the ordinances thereof, the power of godliness is manifest.
21 And without the ordinances thereof, and the authority of the priesthood, the power of godliness is not manifest unto men in the flesh..."  (Doctrine and Covenants | Section 84:19 - 21)

And it is important to also understand, as Paul instructs -

"...no man taketh this honour unto himself, but he that is called of God, as was Aaron."  (New Testament | Hebrews 5:4)

For -

"We believe that a man must be called of God, by prophecy, and by the laying on of hands by those who are in authority, to preach the Gospel and administer in the ordinances thereof."  (Pearl of Great Price | Articles of Faith 1:5)

I hold the Melchizedek priesthood and can trace my lineage of authority back to the Savior.