Knowing full well I am wading into deep waters, it is time to set the record straight on what the Bible says about the method of baptism.
It is not clear, despite what you have been told.
The reason we call it baptism is because the meaning of the Greek word “baptidzō” has been unclear from the beginning. It means to dip. That could mean dipping completely under the surface of water or dipping from the water to pour on the head. Worse, the preposition “en” does not just mean in. It can also mean by or with.
I wish for two things. First, that churches would stop being so dogmatic on the method. It is fine to decide which method to use in your own church, but you cross a line when you condemn others or deny their legitimacy as believers because of the method of baptism. If you baptize by immersion, do so, and ask new members who were baptized by sprinkling or pouring to be immersed. That’s up to you and them. But, please don’t condemn as outside the faith christians who choose a different mode.
Secondly, I wish that we would all open our eyes to see the deep meanings each mode of baptism illustrates. You may be aware of how the mode you use shows the truths of salvation; you may be surprised that other modes also signify much truth.
Immersion in a tank may be somewhat artificial, but it does show how we have been raised to new life in Christ, how our sins have been bathed away, how the Holy Spirit has soaked into us. Baptism in a river, whether by immersion or dipping and pouring over the head, has the additional symbolism of sins being carried away (downstream) and gone forever. A baptismal font just inside the front door of the church is a daily reminder of what we did at baptism and what it means to be sprinkled with the blood of Christ.
If we are convinced that our mode of baptizing is best, fine. Keep doing it, and keep teaching it. But please drop the pride over being correct, and please do not deny that those who use different modes are in the faith. There is one Lord, one faith, one baptism, and that does not mean that Lord is limited to your understanding of Him, that the faith must match your doctrinal statement, or that baptism is only valid if done in your preferred mode. Baptism is supposed to unite us all.