The fifth Article of Faith formally establishes the basic doctrine of priesthood authority. We understand that God chooses people on earth to represent Him and gives His representatives authority to act in His name. Without priesthood authority, ordinances are not binding beyond this life. For example, without priesthood authority marriages are for this life only and baptisms are an empty form.
The Lord was concerned that the Prophet Joseph Smith and other early saints clearly understand the doctrine of divine authority. In the Doctrine and Covenants He frequently reminded them that His servants had to be properly authorized to perform His works.
The Lord has made it clear that He will accept only those ordinances performed by the proper authority, which is His priesthood. We learn from D&C 107:8, "The Melchizedek Priesthood holds the right of presidency, and has power and authority over all the offices in the church in all ages of the world, to administer in spiritual things."
Each phrase in the fifth Article of Faith adds a special bit of meaning. I would like to share some of my thoughts on each phrase.
"We believe that a man must be called of God"
Priesthood authority comes directly from God himself. Prophets are a necessary link in the priesthood chain between God and man. When I was ordained to the Melchizedek Priesthood I received a priesthood line of authority indicating how my priesthood authority comes from God. My father laid his hands on my head and ordained me. He was ordained by my grandfather. The line of priesthood authority goes back several generations to the Prophet Joseph Smith, who received his priesthood from Peter, James, and John. They received their priesthood directly from the Lord Jesus Christ.
The Spirit plays an important part in the callings we receive. Bishops and stake presidents seek inspiration when calling members to fill different Church positions. We should recognize that those who are called to Church offices are called by the spirit of prophecy and we should support them as such.
"...by the laying on of hands by those who are in authority"
Laying on of hands is the method given by God to transfer priesthood authority. Only those who have authority can confer it on someone else. No one can pass on authority that they themselves do not have. When the apostles were killed their authority was lost from the earth. This made it necessary for this authority to be restored again to the earth. It was appropriate for Peter, James, and John to restore the priesthood because they previously held it and they held the keys to this authority. Joseph Smith could not have declared himself a representative of God or performed any valid ordinances without having priesthood authority given to him by someone who was in possession of it and authorized to confer it upon him.
"...to preach the Gospel"
I think this phrase specifically refers to missionaries, or official representatives of the Church. We do not need a special calling or priesthood authority to share the gospel with other people. However, for one to officially represent the Church, a special calling is required. When I was set apart as a missionary, I knew that I was a representative of Jesus Christ. I felt sorrow when people rejected me and rejected the gospel because they were not just rejecting or accepting me personally, they were rejecting or accepting Jesus Christ who I represented.
"...and administer in the ordinances thereof."
We know that we cannot return to Heavenly Father without first receiving essential ordinances that He has given us. If these ordinances are not performed by those who have the proper authority, they are not recognized or accepted by the Lord and are ineffective.
I am thankful that I have the opportunity to hold the Melchizedek Priesthood. I am grateful to have a priesthood line of authority that shows that my priesthood comes from Jesus Christ. I know that without the proper priesthood authority we cannot perform ordinances that will be acceptable to Heavenly Father. This gives me a responsibility to live worthy of the priesthood I hold. This gives all of us the responsibility to share the gospel with others so that they may also receive the blessings that come through the ordinances of the gospel.