Vayikra: Chapter 32
The Holy One, blessed be He, decrees a sentence and the righteous man nullifies it

We learn that the rainbow appears in the sky as a sign of God's protection only when there is no righteous man in the world to protect the world with his prayer. In Rabbi Shimon's day the world did not need the sign of the rainbow, for he himself could nullify any decree that was pronounced over the world. So God decrees and the just man nullifies. When God sees that men perform good deeds, the face of Atika Kadisha is revealed in Zeir Anpin, and everyone is blessed. When transgressions increase in the world, the Ancient One is concealed; this is how the wicked turn mercy into judgment.