Is baptism necessary?
"In baptism we are given to the Lord as a vessel to be used. Baptism is a most solemn renunciation of the world. Self is by profession dead to a life of sin." SDA Bible Commentary, vol. 6, p. 1074.8
"Christ made baptism the entrance to His spiritual kingdom. He made this a positive condition with which all must comply who wish to be acknowledged as under the authority of the Father, the Son, and the Holy Ghost." Manuscript 27a, 1900.6
"The Father, the Son, and the Holy Ghost, powers infinite and omniscient, receive those who truly enter into covenant relation with God. They are present at every baptism, to receive the candidates who have renounced the world and have received Christ into the soul temple." Manuscript 27a, 1900.10
In the Adventist Church, all members join through baptism by immersion or by profession of faith—if they have been baptized by immersion in some other church and wish to be rebaptized by immersion. As the Scriptures and Quotations that follow attest, baptism is more than a perfunctory exercise quickly forgotten. Careful preparation is made to assure that the candidate has studied and accepted the beliefs of the church. Baptism represents several things, including (1) a public declaration of becoming a follower of the Lord Jesus; (2) the public funeral of the old man, and the resurrection of the “new man” per Romans 6:1-11; (3) baptism a public declaration of an unreserved surrender to God; (4) a covenantal ceremony in which the new member pledges his life to God, and the triune members of the Godhead who are present pledge their powers on behalf of the new convert; (5) and an outward symbol of an inward change. Baptism is not magical, however. To receive the benefit of baptism, the individual needs to continue cooperating with God—continuing to die to self, continuing to obey, continuing to remain in a strong relationship with God. In some limited cases where an member has fallen away from their relationship with Christ, the individual may request to be rebaptized. —Dan
Matthew 3:13-15 (NKJV) "Then Jesus came from Galilee to John at the Jordan to be baptized by him. 14 And John tried to prevent Him, saying, “I need to be baptized by You, and are You coming to me?” 15 But Jesus answered and said to him, “Permit it to be so now, for thus it is fitting for us to fulfill all righteousness.” Then he allowed Him."
Matthew 28:18-20 (NKJV) "And Jesus came and spoke to them, saying, “All authority has been given to Me in heaven and on earth. 19 Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, 20 teaching them to observe all things that I have commanded you; and lo, I am with you always, even to the end of the age.” Amen."
Romans 6:4 (NKJV) "Therefore we were buried with Him through baptism into death, that just as Christ was raised from the dead by the glory of the Father, even so we also should walk in newness of life."
Colossians 2:12 (NKJV) "buried with Him in baptism, in which you also were raised with Him through faith in the working of God, who raised Him from the dead."
"In baptism we are given to the Lord as a vessel to be used. Baptism is a most solemn renunciation of the world. Self is by profession dead to a life of sin. The waters cover the candidate, and in the presence of the whole heavenly universe the mutual pledge is made. In the name of the Father, the Son, and the Holy Spirit, man is laid in his watery grave, buried with Christ in baptism, and raised from the water to live the new life of loyalty to God. The three great powers in heaven are witnesses; they are invisible but present." SDA Bible Commentary, vol. 6, p. 1074.8
"Baptism is a sacred rite, instituted by Christ, by which the human agent is dedicated to God. The ordinances of baptism and the Lord’s supper are two monumental pillars, one within and one without the church. Upon these ordinances Christ has inscribed the name of the true God. Manuscript 27a, 1900.5 …
Christ made baptism the entrance to His spiritual kingdom. He made this a positive condition with which all must comply who wish to be acknowledged as under the authority of the Father, the Son, and the Holy Ghost. Those who receive the ordinance of baptism thereby make a public declaration that they have renounced the world and have become members of the royal family, children of the heavenly King. Manuscript 27a, 1900.6 ...
Those who are baptized in the threefold name of the Father, the Son, and the Holy Ghost, at the very entrance of their Christian life declare publicly that they have accepted the invitation, “Come out from among them, and be ye separate, ... and touch not the unclean thing; and I will receive you, and will be a Father unto you, and ye shall be my sons and daughters, saith the Lord Almighty.” “Having therefore these promises, dearly beloved, let us cleanse ourselves from all filthiness of the flesh and of the Spirit, perfecting holiness in the fear of the Lord.” “If ye then be risen with Christ, seek those things which are above, where Christ sitteth on the right hand of God.” Manuscript 27a, 1900.8 …
The Father, the Son, and the Holy Ghost, powers infinite and omniscient, receive those who truly enter into covenant relation with God. They are present at every baptism, to receive the candidates who have renounced the world and have received Christ into the soul temple. These candidates have entered into the family of God, and their names are inscribed in the Lamb’s book of life. Manuscript 27a, 1900.10 …
The Lord designs His church below to be a place where heaven is personified. Christ said, “Where two or three are gathered together in my name, there am I in the midst of them.” The three highest powers of heaven combined to organize a church composed of members who would be distinguished from world-lovers and world-servers by the spiritual nature of their profession and their practical godliness. Manuscript 27a, 1900.13 …
Three distinct agencies, the Father, the Son, and the Holy Ghost, work together for human beings. They are united in the work of making the church on earth like the church in heaven. They place the resources of heaven at the disposal of those who will appreciate and impart these spiritual treasures, multiplying them by using them to the glory of God. Every diligent effort to improve adds to the gifts we have. The powers of heaven work with human beings on the plan of multiplication." Manuscript 27a, 1900.22
"Provision has been made that when man repents and takes the steps requisite in conversion, he shall be forgiven. When he is baptized in the name of the Father, the Son, and the Holy Ghost, these three great powers are pledged to work in his behalf. And man on his part, as he goes down into the water, to be buried in the likeness of Christ’s death and raised in the likeness of His resurrection, pledges himself to worship the true and living God, to come out from the world and be separate, to keep the law of Jehovah." Manuscript 31, 1901.12
"Those who are baptized in the threefold name of the Father, the Son, and the Holy Spirit, at the very entrance of their Christian life declare publicly that they have forsaken the service of Satan and have become members of the royal family, children of the heavenly King." Testimonies for the Church, vol. 6, p. 91
"You are baptized in the name of the Father, of the Son, and of the Holy Ghost. You are raised up out of the water to live henceforth in newness of life--to live a new life. You are born unto God, and you stand under the sanction and the power of the three holiest Beings in heaven, who are able to keep you from falling. You are to reveal that you are dead to sin; your life is hid with Christ in God. Hidden "with Christ in God"--wonderful transformation. This is a most precious promise. When I feel oppressed and hardly know how to relate myself toward the work that God has given me to do, I just call upon the three worthies, and say: You know I cannot do this work in my own strength. You must work in me, and by me, and through me, sanctifying my tongue, sanctifying my spirit, sanctifying my words, and bringing me into a position where my spirit shall be susceptible to the movings of the Holy Spirit of God upon my mind and character. And this is the prayer that every one of us may offer." Sermon and Talks, vol. 1, p. 367.3
"After the believing soul has received the ordinance of baptism, he is to bear in mind that he is dedicated to God, to Christ, and to the Holy Spirit. These three all co-operate in the great work of the covenant made by baptism in the sight of the heavenly universe. The Father, the Son, and the Holy Spirit receive the believing soul into covenant relation with God." Manuscript 56, 1900.26
"In receiving baptism, the human agent, inspired with new purposes, pledges himself to die to the world and live in obedience to Christ. The Father, the Son, and the Holy Ghost supply the power that makes him victorious in every conflict with the prince of darkness."—Letter 200, 1902, p. 7. (To Brother and Sister Kress, December 15, 1902)." Manuscript Releases, vol. 6, 167.2
"At the baptismal ceremony we virtually take a most solemn oath in the name of the Father and of the Son and of the Holy Ghost, that henceforth our lives will be merged into the life of these three great individual Agencies; that the life we now live in the flesh we will live in faithful obedience to God’s sacred and holy law, keeping all His statutes and His commandments; that we will live in newness of life as men and women having a new birth unto God. We, as new born souls born to live in newness of life, acknowledge God’s covenant, that [we] are in reality pledging ourselves by a solemn oath to seek henceforth those things which are above where Christ sitteth on the right hand of God. By our profession of faith we acknowledge the Lord as our God, and pledge ourselves to obey His commandments." Manuscript 68, 1900.12
"When we were baptized “in the name of the Father, and of the Son, and of the Holy Ghost,” these three great powers pledged themselves to work in our behalf as we strove to live the new life in Christ. And in receiving baptism, the human agent, inspired with new purposes, pledges himself to die to the world and live in obedience to Christ. The Father, the Son, and the Holy Ghost supply the power that makes him victorious in every conflict with the prince of darkness." Letter 200, 1902.20
Though there is often a desire to hurry candidates into the baptismal tank, it is wise to take time to make sure the individually is thoroughly prepared. Recall that baptism is a solemn renunciation of the world, coming into covenantal relationship with the triune Heavenly Powers and an unreserved surrender for the rest of one's life to God. Until a person has come to the point, they are not really prepared to be baptized.—Dan
This page shares the blessings that come with baptism.
You should read about rebaptism as well.