Hebrews 2:1 "For this reason"

Hebrews 2:1
δια τουτο δει περισσοτερως ημας προσεχειν τοις ακουσθεισιν μηποτε παραρρυωμεν

"For this we must pay increasingly great attention to what we have heard, lest it slips away from us".

For the author of Hebrews, the matter he refers to when he says "For this" is so clear, he doesn't identify it. Most modern English translations insert the clarifying word "reason": "For this reason".

What is that reason?

It is the reason given in Hebrews 1:5-14: That the Son is entirely and absolutely God, the Son receives the praise and acclamation of God, is called YHWH by YHWH Himself, and thus is infinitely greater than all the angels or beings who in the past have spoken on behalf of God.

"What we have heard"

The author of the epistle has just quoted several verses from the Old Testament where God spoke to the Son acclaiming Him as Son and God. That which "we have heard" is no other than the voice of God proclaiming before all creation the full divinity of His Son. For us as modern readers it is most astounding that the writer of this epistle considered the sacred writings from the Psalms as the voice of God. The written word in the psalms is now proclaimed as the voice of God which "we have heard". The written word is to be paid increasing heed as the voice of God which if disregarded, may not come back to the hearer. However, it is the message of that spoken voice which may slip away from the hearer. That message is that the voice of the Father establishes the infinite superiority and supremacy of the Son over all creation and recognized in full equality with God.

The author enjoins the readers not to let this sovereign truth slip away from their hearing. They must constantly tune in and keep on hearing it. That truth is that the Son is supreme as God's authority and revelation to humanity. Christ's supremacy is the center to which we must take firm hold and not let that truth slip away from us.