"Both passages quoted above refer to the ceremonial law of the Old Testament and that the eternally binding moral law. Christ, however, is declared in His gospel to be the end of or the aim of both, so that the law functions for believers as their schoolmaster to bring them unto Christ (Gal.3:24).
However, the revelation of the gospel of salvation was not limited to this. God, who in earlier times had caused it to be proclaimed to the believing fathers, has lastly "Fulfilled it by His only begotten Son." He sent Christ, His Son, into the world in the fullness of time to accomplish the salvation of the elect both passively and actively, so that thereupon He would be exalted to be the ruler, the king, and the savior of His people.
Thus, the instructor posits that by means of this holy and precious gospel, a gospel that God has revealed to the world and at His time brought to fruition, believers may know with certainty that the Lord Jesus Christ is the true mediator and deliverer to whom all the ends of the earth must turn in order to be saved (Isa.45:22). In so doing, the instructor has identified and unveiled the one mediator, who, on behalf of guilty and impotent sinners such as we are, is capable and all-sufficient to satisfy God's justice and to deliver us from all our misery, into which, by our sins, we have sunk as into a bottomless pit.
However, the mere knowledge that there is such a mediator and deliverer for us will be of no help to us if we do not truly and personally turn unto Him and His redemption. As impotent sinners, we need to surrender ourselves fully unto Him for salvation, thereby securing true union and communion with Him by faith. . ." pg.83.84 Theodorus VanderGroe