'Prove' in the Bible

No, indeed; let us hold God to be true, though every man should prove to be false. As it stands written, "That Thou mayest be shown to be just in the sentence Thou pronouncest, and gain Thy cause when Thou contendest."

It was to demonstrate His righteousness at the present time, so that He would be just and the One who justifies those who have faith in Jesus [and rely confidently on Him as Savior].

Did that which is good [the Law], then become death to me? Certainly not! But sin, in order that it might be revealed as sin, was producing death in me by [using] this good thing [as a weapon], so that through the commandment sin would become exceedingly sinful.

And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God.

that I may be rescued from those who are disobedient in Judea, and that my service for Jerusalem may prove acceptable to the saints;