The first words from Jacob, Nephi's brother, are marvelous. He begins his public ministry among the people of Nephi with these words:
"I, Jacob, having been called of God, and ordained after the manner of his holy order, and having been consecrated by my brother Nephi," (2 Ne. 6: 2.)
Jacob was "called of God." He was also "ordained after the manner of his holy order," meaning that his ordination came from God. He was like Melchizedek. The manner of this ordination is described in JST-Gen. 14: 27-29: "[H]aving been approved of God, he was ordained an high priest after the order of the covenant which God made with Enoch, It being after the order of the Son of God; which order came, not by man, nor the will of man; neither by father nor mother; neither by beginning of days nor end of years; but of God; And it was delivered unto men by the calling of his own voice, according to his own will, unto as many as believed on his name." This was the holy order to which Jacob was called by God.
In the restoration of the Gospel, the first time this appeared in the church was in June, 1831 on Isaac Morley's farm. As Joseph Smith recorded it in his history: "the authority of the Melchizedek Priesthood was manifested and conferred for the first time upon several of the Elders. It was clearly evident that the Lord gave us power in proportion to the work to be done, and strength according to the race set before us, and grace and help as our needs required." (DHC 1: 175-177.) To understand this statement of Joseph you would need to recognize there is a great difference between being "an Elder in the church"-- an office held by operation of the church's organization, much like a Relief Society President or a Sunday School President-- and the Melchizedek Priesthood. Today there is no appreciation of that distinction. That is because we have little understanding of the history of the church or the scriptures.
In any event, Jacob was ordained by God to "his holy order" or, in other words, received the same High Priesthood as Melchizedek in the only way it can be received: "It [is] delivered unto men by the calling of His own voice." Jacob was one of those.
Despite this, Jacob's right to be a teacher among the people of Nephi reckoned from his brother's presiding authority. Although Jacob was in possession of this calling from God, in order to minister to the people he needed to also be "consecrated by my brother, Nephi." It was Nephi who was the presiding authority. Therefore, to preach to the congregation Jacob needed to be called and authorized. Nephi did this, and Jacob became a recognized, sustained teacher.
Without both, Jacob could have preached, taught and expounded, but he would not be able to speak in an organized meeting of the church over which Nephi presided. From this we see the order of things. The church and God's authority do not necessarily overlap. But, in his wisdom, Nephi used the very man who God had empowered to be a minister of righteousness within the church over which Nephi presided. Nephi did not envy his younger brother's calling, but supported and advanced him in it. Of course Nephi held the same calling, but that does not matter. Somehow men can find it within them to be jealous of others even if they are called themselves. After all, Lucifer was a son of the morning.
Joseph Smith, by revelation in January, 1841, was told that his brother Hyrum was to become "a prophet, and a seer, and a revealtor unto my church." (D&C 124: 94.) Joseph did not envy his brother this calling, but immediately ordained him to the office of Assistant President; in an almost identical manner as had Nephi with his brother Jacob.
From the first phrase out of Jacob's mouth, we encounter doctrine so very meaningful to understanding the way of God. What a great book we have in the Book of Mormon. I do think a man can get closer to God by abiding its precepts than from any other book!