Moses de Leon, Shushan ‘Edut, pp. 363-364

Jewish Mysticism
Whenever the rainbow is seen in the cloud, then the sign of the covenant is within her and the judgment vanishes from the world…. The secret is “I will remember My covenant” (Gen. 9-15), for there is no memory (zekhirah) without the sign of the covenant (’ot berit). Therefore they established the blessing [on the rainbow], “Blessed be the one who remembers the covenant” (zokher ha-berit), for then she contains all the colors that are seen within her from [the gradation that is called] the All. Thus, God, blessed be He, has mercy over the creatures and over the earth. Know that the secret of the matter of the rainbow and [that of] the covenant are joined together. Therefore, they established that it is forbidden for a person to look at the rainbow in order not to cause shame to the Shekhinah and not to look within her. Thus the prophet said, “Like the appearance of the bow (kemar’eh ha-keshet) that shines in the clouds on a day of rain, such was the appearance of the surrounding radiance. That was the appearance of the semblance of the glory of the Lord” (Ezek. 1-28).

Translated by Elliot Wolfson in “Re/membering the Covenant- Memory, Forgetfulness, and History in the Zohar,” in Jewish History and Jewish Memory- Essays in Honor of Joseph Hayim Jerushalmi, 214-246. Edited by E. Carlbach, D. S. Myers, and J. Efron. Hanover and London- Brandeis University Press, 1998.