Jacob is talking about magnifying his calling in the priesthood.
Joseph Fielding Smith
"Every man who is ordained to an office in the Melchizedek Priesthood should realize fully just what that ordination means. He receives the Priesthood with an oath and covenant that he will magnify his calling and be faithful therein.
Joseph F. Smith
"Think what it means to hold keys of authority which-if exercised in wisdom and in righteousness-are bound to be respected by the Father, the Son, and the Holy Ghost! Do you honor this Priesthood? Do you respect the office and honor the key of authority that you possess in the Melchizedek Priesthood, which is after the order of the Son of God? Will you, who hold this Priesthood, profane the name of Deity? Would you be riotous, and eat and drink with the drunken, with the unbelieving and with the profane? Would you, holding that Priesthood, forget your prayers, and fail to remember the Giver of all good? Would you, holding that Priesthood, and possessing the right and authority from God to administer in the name of the Father, and of the Son, and of the Holy Ghost, violate the confidence and the love of God, the hope and desire of the Father of all of us? For, in bestowing that key and blessing upon you, he desires and expects you to magnify your calling. Would you, as an elder in the Church of Jesus Christ, dishonor your wife or your children? Would you desert the mother of your children, the wife of your bosom, the gift of God to you, which is more precious than life itself? For without the woman the man is not perfect in the Lord, no more than the woman is perfect without the man." (Gospel Doctrine, p. 165)