Note 12 at Eph 2:17: This verse seems to be an allusion to Isa 57:19. Through Jesus, mankind can now be reconciled (see note 11 at 2Co 5:18) to God and to each other.

It is "through him"--Jesus Christ (Eph 2:18) and His death--that Jew and Gentile alike may now come boldly unto His throne of grace (Heb 4:16). The Gentiles, who were far off "having no hope, and without God in the world" (Eph 2:12), and the Jews, who were near because of the covenants of promise, are now in Christ Jesus (Eph 2:13). How much better it is to be in Christ Jesus than just to be near.

Prior to this, Jews could approach God through their mediator, the high priest, and Gentiles could approach God by their conversion to Judaism. But now Jesus has become the door whereby all people may come to God solely on the basis of faith in what He has done for them.