When the Lord proclaims there is a "doctrine" belonging to Him, it is important to take note. As He begins His doctrinal statement, He first reminds us again of the unity between Himself, His Father and the Holy Ghost. This reminder of unity has followed the admonition to avoid contention and anger - things which prevent our becoming one with each other.
To understand His doctrine you must first know and understand that the doctrine originates with the Father. Christ has completely accepted and advocates the doctrine. Moreover He embodies it.
The Father's doctrine is that "all men, everywhere, [must] repent and believe in [Christ]." This is what the whole of creation hangs on: the atonement of the Son. It is through the Son's sacrifice that the Father's plan became operational. Now, to return to the Father all must do so in reliance upon the merits of the Son. (John 3: 16.)
The Son preaches the doctrine of, and bears witness of the Father. The Father bears witness of the Son. The Holy Ghost bears record of the Father and Son.
When did the Father bear record of the Son? Did you notice that? The FATHER bears record of the Son! I'm not talking about Matthew or Luke's testimony that the Father bore record of the Son, because that is Matthew's and Luke's testimony. I'm not talking about Joseph Smith's record of the Father's testimony of the Son. I'm talking about the Father's testimony. When did you hear the Father bear record of the Son?
The Father does bear record of the Son. But you must go through the Son to get to the Father. When you do, acting in faith according to the conditions established for your salvation, then you will receive the Father's testimony or record of the Son for yourself. But implicit in this statement is the fact that access to the Father is possible by the means provided through the Son. That is a ratification of the fullness of the Gospel. It is an invitation to return to heaven and obtain from the Father a confirmation of your salvation.
The Father's testimony is that our salvation comes through Christ. For us the Father has provided a Savior. If we repent, we can come back into the presence of God and enter into our salvation and exaltation. But it is through the means provided for us: A Savior, who is Christ the Lord.
We are commanded to:
To repent is to turn again to Him. To follow Him and leave behind your sinful ways. To abandon the world and worldliness and to choose to always remember Him, that you may have His spirit to be with you always.
To believe in Him is to accept, study, contemplate and ponder His teachings. It is not to just go along with a herd, but to rise up from your position and awaken from your slumber. It is to grow into knowledge about Him. Belief leads to faith and faith to knowledge. But the process is initiated by your belief (correct understanding) of His teachings.
The doctrine continues...