In Whom you also –
on hearing the word of truth,
the evangel of your salvation –
in Whom on believing also,
you are sealed with the holy spirit of promise
-Ephesians 1:13-
Paul reminds the "believers in Christ Jesus" (1:1) that they are sealed with the holy Spirit. That happened when they heard the word of truth and believed it. Concerning this Word it is elsewhere testified that it is "Spirit and life" (John 6:63). Consequently, when this Word finds entrance, the Spirit is with it and remains, because it is a "sealing" from God's side, which cannot be undone by no one and by nothing.
What is that word of truth? Paul explains: it is the Evangel of your salvation! So, before they believed, they were made acquainted with the good tiding of their salvation! Do you realize what that means? At standard-evangelism, you get to hear the Evangel of your salvation after you have become a believer. That is for Paul not the word of truth. The truth is that God is your and everyone's Saviour (1Tim.4:10). "For the grace of God hath appeared, bringing salvation to all men…" (Tit.2:11). That is the Word of truth and the Evangel that should be preached and believed. Not because God would become our Saviour, but because God is our Saviour!
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Translation: Peter Feddema