5 And now, if the Lamb of God, he being holy, should have need to be baptized by water, to fulfil all righteousness, O then, how much more need have we, being unholy, to be baptized, yea, even by water!
6 And now, I would ask of you, my beloved brethren, wherein the Lamb of God did fulfil all righteousness in being baptized by water?
7 Know ye not that he was holy? But notwithstanding he being holy, he showeth unto the children of men that, according to the flesh he humbleth himself before the Father, and witnesseth unto the Father that he would be obedient unto him in keeping his commandments. (2 Nephi 31)
I have heard people use this scripture to explain that the reason why we are baptized is to have our sins washed away and that we have to have our sins washed away in this manner because we are so much more sinful than Christ. But this isn’t why Christ was baptized, and it isn’t the reason why we are baptized, either.
Nephi tells us in plainness why Christ was baptized. He was baptized “to fulfill all righteousness”, to “humbleth Himself before the Father, and witnesseth unto the Father that he would be obedient unto him in keeping his commandments.” Christ was not baptized in water to be cleansed of any sin. Water baptism, by itself, does not cleanse any person from his sins. It didn’t for Christ and it doesn’t for us, either. It was a commandment from the Father that stood as a witness that Christ would be obedient to all of God’s commandments.
But, wait! Was Christ’s life before his baptism rebellious or sinful in any way? No, it wasn’t. He had already demonstrated perfect obedience to God. He, being holy, didn’t need a singular event like a water baptism to mark the point in his life at which he would begin to be obedient. Christ submits to baptism because it is a commandment from the Father and He obeys ALL of the Father’s commandments.
We, on the other hand, being unholy, rebel and commit sin pretty regularly. The Father commands us to be baptized to demonstrate that we are willing to submit to his commands. What better way to proclaim publicly that we are willing to obey God’s commands than to actually obey one of His commands? It is an act of submission, faith, trust, obedience, and humility. It marks the point at which we become willing to “...follow the Son, with full purpose of heart, acting no hypocrisy and no deception before God, but with real intent, repenting of your sins, witnessing unto the Father that ye are willing to take upon you the name of Christ...”. (2 Nephi 31:13) We “follow the Son” when we enter the waters of baptism with same conditions of the heart—the same “full purpose of heart”, the same lack of hypocrisy, the same lack of deception before God, and the same “real intent”— that Christ had when He was baptized.
Christ was baptized because he is obedient to all of God’s commands and we should be baptized once we are willing to obey all of God’s commands, too.