Praedicatio Verbi Dei Verbum Dei est: The preaching of the Word of God is the Word of God.Richard Muller, Dictionary of Latin and Greek Theological Terms: Drawn Principally From Protestant Scholastic Theology, Term: Praedicatio Verbi Dei Verbum Dei est.
For the Protestant Scholastics and for us here at StandardSacredText.com, there are three ways in which we speak of the word of God.
(1) The Archetypal Word of God: This is Jesus Christ, the Word that was made flesh and that dwelt among us. Archetypal speaks of a founding type or the type from which all other types come [e.g., prototype and ectype]. Because Christ is the archetypical Word, the Logos, all other revealed words come from Him and specifically by the One Jesus sent – the Holy Spirit.
(2) The Revealed word of God: This is the audible voice of God, the words of the prophets, the message of the apostles, and in our time, the written inspired Scriptures of the Old and New Testament. When comparing Christ and Scripture we distinguish these two as the Word of God and the word of God respectively. In other news, the same goes for God as Canon and the Scriptures as canon.
(3) The Preached word of God: This of course is most relevant to the above quote. The idea is that the Scriptures are the living voice of God in that the living God, the Holy Spirit, speaks through the word to the saint toward sanctification and to the lost toward repentance or judgment. Thusly construed, when the revealed word is preached, the living God in the person of the Holy Spirit speaks in concert with His own words through the preaching. In such cases and under such circumstances the preaching of the word of God is itself the word of God. This is why preachers should simply preach and teach what the Bible says instead of playing Oprah or Dr. Phil or Jordan Peterson or the latest movie with a mildly redemptive theme.