D&C 21

 As the Church was being organized, the Prophet Joseph Smith received this revelation - 

"Behold, there shall be a record kept among you; and in it thou shalt be called a seer, a translator, a prophet, an apostle of Jesus Christ, an elder of the church through the will of God the Father, and the grace of your Lord Jesus Christ,

2 Being inspired of the Holy Ghost to lay the foundation thereof, and to build it up unto the most holy faith."  (Doctrine and Covenants 21:1–2)

Being called as an elder, we are taught - 

"The name of an office in the Melchizedek Priesthood, elder is also the general title used to address one who bears this priesthood. Elder Bruce R. McConkie added that an elder is a representative of the Lord: 

“What is an elder? An elder is a minister of the Lord Jesus Christ. He holds the holy Melchizedek Priesthood. He is commissioned to stand in the place and stead of his Master—who is the Chief Elder—in ministering to his fellowmen. He is the Lord’s agent. His appointment is to preach the gospel and perfect the Saints.” (“Only an Elder,” Ensign, June 1975, p. 66.) (End of quote from the Doctrine and Covenants Student Manual, 1981 edition, p. 44.)