Baptism is an ordinance observed by those who have placed their trust in Jesus Christ as Lord and Saviour. It is observed in obedience to His express command:
"Go therefore and make disciples of all nation baptizing them in the name of the Father and the Son and the Holy Spirit" (Matthew 28:18-20)
Baptism follows salvation. It does not contribute to salvation as the Apostle Paul clearly states:
"For by grace you have been saved through faith, and that not of yourselves; it is the gift of God" (Eph 2:8,9)
The English word "baptize" is a term borrowed from the New Testament Greek, baptidzo, meaning to dip or immerse. Baptism by immersion was the biblical practice:
And both Philip and the eunuch went down into the water, and he baptized him. Now when they came up out of the water" (Acts 8:36-39)
Baptism by immersion carries a visual portrayal of a spiritual reality, true of all believers in Christ. The believer has been placed into Christ.
"For by one Spirit we were all baptized into one body; whether Jews or Greeks, whether slaves or free; and have all been made to drink into one Spirit." (1 Cor. 12:13)
The Bible teaches that every believer is thus identified with Christ in His death, burial, and resurrection.
"Do you not know that so many of us as were baptized into Jesus Christ were baptized into His death? Therefore we are buried with Him by baptism into death: that just as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life. For if we have been united together in the likeness of His death, certainly we shall also be in the likeness of his resurrection" (Romans 6:3-5)
As Christ went down into death so the believer is lowered below the water. As Christ rose from the dead, so the believer is raised out of the water. Baptism therefore signifies a new beginning, the beginning of a new life in Christ.