The word “Trinity” is never used in the Bible, BUT the concept of the Trinity is found throughout the Bible. The concept of water baptism being a symbolic act of obedience is not found anywhere in the Bible. The Bible does not teach that water baptism is a symbolic act of obedience, but our Baptist churches teach that doctrine anyway—based upon experience and tradition rather than the Scriptures. On one side of their mouths, our Baptist churches teach a doctrine based upon experience and tradition rather than upon the Scriptures, and on the other side of their mouths they hypocritically teach the non-biblical doctrine of sola scriptura!
There is no concept of the Trinity nor Baptism in scripture. There is however a clear doctrine taught about both in scripture. Just because we use words not specifically used in scripture to refer to a clear doctrine taught in scripture in no way negates that teaching nor does it reduce that doctrine to a mere "concept".
The doctrine of Baptism is taught in scripture in very clear terms when we read Romans 6:
Rom 6:3 Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death?
Rom 6:4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
Rom 6:5 For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection:
Rom 6:6 Knowing this, that our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin.
Rom 6:7 For he that is dead is freed from sin.
Rom 6:8 Now if we be dead with Christ, we believe that we shall also live with him:
Rom 6:9 Knowing that Christ being raised from the dead dieth no more; death hath no more dominion over him.
Rom 6:10 For in that he died, he died unto sin once: but in that he liveth, he liveth unto God.
Rom 6:11 Likewise reckon ye also yourselves to be dead indeed unto sin, but alive unto God through Jesus Christ our Lord.
It is clear Paul is speaking of the symbolism of Baptism when he connects its parts to the death, burial, and resurrection of Christ. This he did to show the public confession of commitment we make when we get Baptized. Just as the old man was buried of Christ so should ours be. Just as Christ was raised from the grave so are we when we come up out of the water and are new.
This is not mere experience nor is it tradition. This is a "rock solid" doctrine taught in scripture with no ambiguity involved. This is no just a concept it is however the word of God.