As we read the Bible we note that God loves role-plays. Passover is a wonderful example - year after year, the children of Israel play out what happened at Passover. The whole wilderness journey is expressed in the role play at the feast of Sukkoth. Others played out a role in their life - take Hosea for example, who demonstrated the sinfulness of Israel .
Baptism also has been instituted to remind us of many deep and meaningful thoughts, but in essence it is a symbol where the one being baptised, announces to those around her, that she indeed is a child of God: a new creation, the old being done away followed by a walk according to that of Jesus Christ, of course, aided by the Spirit of God.
So what is Baptism?
The Apostle Paul in the letter to the church in Ephesus says there is one Baptism - as there is also one God and Father of all.
It was also the Apostle Paul that sets out the doctrine of Baptism when writing to the Romans: He says in chapter 6:
Do you not know that as many of us as were baptized into Christ Jesus were baptized into His death? 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.
So baptism is of the individual, done once.
Baptism is done unto the significance of His death - the death of Jesus Christ. Baptism does not confer salvation - indeed it cannot save. It does not confer membership of the church.
It does however highlight three elements of the doctrine of Salvation.
It emphasizes death - this the Apostle Paul draws out - it actually highlights two deaths - the death of Jesus Christ who saves us, and the death of our old nature.
Baptism emphasis burial - someone who is rightly dead is buried - it is the closure of any death, and hence we understand that the death is real. I believe that immersion into a body of water is the true symbolism needed here for death and burial. At this point we are buried with Christ by baptism. Christ also was buried.
However, as Christ rose again to this earth on the third day, and to heaven on the fiftieth day, so there is the element of being raised from the dead in Baptism. Hence Baptism is a figure of the resurrection of Christ: and taking the words of the Apostle Paul writing to the church at Colossi - you were … 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. This part is by the action of God - no one dead can raise on his own accord.
Therefore we note there is no effort on the part of the one being baptized - it is the effort of the baptizer that creates the symbol, which underscores that being saved is an act of faith upon God, not upon one's own goodness, for we all have none (see Ephesians 2).
And what is one Baptised unto: As Jesus said to Nicodemus - only by being born again can one enter the kingdom of heaven - Baptism symbolizes that the old is buried; we are to walk from that day forth in the "newness of life". Again, the Apostle Paul:
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.
We baptise and are baptised in obedience to God's command - this is repeated many times in the New Testament.
And Jesus came and spoke to them, saying, 'All authority has been given to Me in heaven and on earth. 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, 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." Matthew 28:18 - 20