Albert Barnes on Ephesians 2:18

For through him. That is, he has secured this result that we have access to God. This he did by his death--reconciling us to God; by the doctrines which he taught--acquainting us with God; and by his intercession in heaven--by which our "prayers gain acceptance" with him.

We both have access. Both Jews and Gentiles.

Rom 5:2. We are permitted to approach God through him, or in his name. The Greek word here--προσαγωγη--relates, properly, to the introduction to, or audience which we are permitted to have with a prince or other person of high rank. This must be effected through an officer of court to whom the duty is entrusted. Rosenmuller, Alt. und neu. Morgenland, in loc.

By one Spirit. By the aid of the same Spirit--the Holy Ghost. 1Cor 12:4.

Unto the Father. We are permitted to come and address God as our Father. Rom 8:15,16.

(b) "through him" Jn 14:6, 1Pet 3:18