Why do I need to be baptized if I have already accepted Jesus as my Savior?

Jesus has commanded that all who accept Him and want to come to Him must be baptized.  Jesus told Nicodemus, “Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God (John 3:5).  To be born of water means to be baptized and to be born of the Spirit means to receive that Holy Spirit as your constant companion.  The Book of Mormon teaches this very clearly:

“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!  And now, I would ask of you, my beloved brethren, wherein the Lamb of God did fulfil all righteousness in being baptized by water?  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 31:5-7).”

Even Jesus had to be baptized in order to continue being perfectly righteous.    In the Book of Mormon Jesus says to the ancient inhabitants of the Americas:

” And no unclean thing can enter into his kingdom; therefore nothing entereth into his rest save it be those who have washed their garments in my blood, because of their faith, and the repentance of all their sins, and their faithfulness unto the end.   Now this is the commandment: Repent, all ye ends of the earth, and come unto me and be baptized in my name, that ye may be sanctified by the reception of the Holy Ghost, that ye may stand spotless before me at the last day (3 Nephi 27:19-20).”

Since everyone has sinned, we are all unclean before God and need to be cleansed of our sins.  To do this, we must come unto Jesus Christ through baptism and then we will receive the Holy Ghost.