In Deuteronomy 30:19 God makes a sovereign promise. He calls heaven and earth as His witnesses. In the words of Gary North:
In this covenant lawsuit, God’s witnesses for either the prosecution or the defense were heaven and earth: the creation. He is the creator of heaven and earth. God is sovereign in His court. ((North, Gary. Inheritance or Dominion: An Economic Commentary on Deuteronomy, Chapter 70 on Life and Dominion))
The covenantal promises or curses were not to be revoked because God’s witnesses could not lie, since they reveal what the Creator desires. The promises were real and concrete. God leaves no room for a supposed neutrality; only life or death.