The mystery of indivisibility is the popular subject of many a metaphysical arguments, yet the Bible declares with divine authority that God is One. And the Hebrew word it uses here is not about number but about oneness, because it speaks of the only true God who is so whole and complete that He cannot be divided.
This God gave His undivided attention to the people He chose from amongst all the nations of the earth to bear His name. They were to have an undivided heart just like His and to live in the land He gave them forever. But, although they proclaimed, “hear O Israel the Lord is our God the Lord is One”, they still needed a new heart. So God’s Messiah died to exchange His undivided heart for their broken ones.
Since then many have chosen His wholeness, whilst others still nurse their brokenness. But when Yeshua* returns, whether Jew or Gentile, disciple of Yeshua or not, all will know that “the Lord is God, the Lord is One”.
* Yeshua is the Hebrew name of Jesus.