What does it mean for a doctrine to be ‘biblical’? Does there have to be a verse expressly stating it? Can we use only biblical words to express it? Is any teaching that departs from the explicit language of the Old and New Testaments thereby suspect? The Old Princeton giant B.B. Warfield helpfully shows us how a doctrine can (and sometimes must) be expressed in un-biblical language and yet be thoroughly scripturally-rooted.
The term “Trinity” is not a Biblical term, and we are not using Biblical language when we define what is expressed by it as the doctrine that there is one only and true God, but in the unity of the Godhead there are three coeternal and coequal Persons, the same in substance but distinct in subsistence. A doctrine so defined can be spoken of as a Biblical doctrine only on the principle that the sense of Scripture is Scripture. And the definition of a Biblical doctrine in such un-Biblical language can be justified only on the principle that it is better to preserve the truth of Scripture than the words of Scripture. The doctrine of the Trinity lies in Scripture in solution; when it is crystallized from its solvent it does not cease to be Scriptural, but only comes into clearer view. Or, to speak without figure, the doctrine of the Trinity is given to us in Scripture, not in formulated definition, but in fragmentary allusions; when we assembled the disjecta membra into their organic unity, we are not passing from Scripture, but entering more thoroughly into the meaning of Scripture. We may state the doctrine in technical terms, supplied by philosophical reflection; but the doctrine stated is a genuinely Scriptural doctrine.
-The Biblical Doctrine of the Trinity, B.B. Warfield
You can read the whole article here. It’s dense at some points and the language is a little dated, but this gem is entirely worth your time.