I think it's important to see what's going on in this very involved sermon text. It's never easy to deal with a passage all tangled up with back-to-back quotations from other sources. These words don't flow with the poetic ease of 1 Corinthians 13 or straight forward instruction of the book of James. But they also carry lessons and benefits other texts don't.
And the great value - and the great difficulty - of our text this morning is we are being taught not only the meaning of this text but the method to find the meaning of other texts - Old Testament texts specifically. That's what the writer emphasizes in those first two verses of chapter one. God spoke in "many ways" at "many times" through many "prophets." But those ways and those times are all finished now. The Son is God's final word. He's the Word all the other revelations were preparing for.
So our writer is laboring to say now that we have the final Word we can see more clearly and accurately what God was up to in all the other words spoken earlier by those prophets. We finally have light shining on all those other texts which couldn't be fully appreciated without beginning with the Incarnate Christ, God the Son.