Doctrine
"Hear, O Israel: The LORD our God is one LORD."
Deuteronomy 6:4
The very first truth God taught His people was not a rule to keep, but a Person to know: that He is one. Every other truth of the faith rests upon this foundation stone.
Against all the idols of the nations, the Word of God speaks with one unbroken voice: the LORD our God is one. He is the only true and living God, and beside Him there is no other.
"Hear, O Israel: The LORD our God is one LORD." (Deuteronomy 6:4)
"I am the LORD, and there is none else, there is no God beside me." (Isaiah 45:5)
When the Lord Jesus Christ was asked which was the first commandment of all, He did not set this truth aside; He confirmed it, and the honest scribe agreed with Him.
"And Jesus answered him, The first of all the commandments is, Hear, O Israel; The Lord our God is one Lord." (Mark 12:29)
This one God is not a lonely, silent unity. In His own Word He has made Himself known as Father, Son, and Holy Ghost — three Persons, and yet one God, not three Gods. This is a mystery too deep for any man to fathom, yet it is plainly written.
"For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one." (1 John 5:7)
At the baptism of the Lord Jesus Christ, all three were present at once: the Son standing in the water, the Holy Ghost descending as a dove, and the Father speaking from heaven. One God, eternally Father, Son, and Holy Ghost.
Here is the wonder at the centre of everything we believe: the one God of Israel came down and was manifest in human flesh in the Person of the Lord Jesus Christ. He is not a second God, nor a lesser God, but the one true God made visible.
"And without controversy great is the mystery of godliness: God was manifest in the flesh." (1 Timothy 3:16)
"I and my Father are one." (John 10:30)
So when we bow before the Lord Jesus Christ, we do not break the first commandment — we keep it. We worship the one God, who has drawn near to save us.
"But to us there is but one God, the Father, of whom are all things... and one Lord Jesus Christ, by whom are all things."1 Corinthians 8:6