את קשתי נתתי בענן והיתה לאות ברית… (נח ט: יג)

Hashem made a pact with Noach that he wouldn’t send a mabul again onto this world and would show a rainbow instead. When one sees a rainbow, one must make the special Bracha to remember the pact between Hashem and Noach ( זוכר הברית ונאמן בבריתו וקיים במאמרו), and the Gemara says that one shouldn’t look at the rainbow for a prolonged time.

The Gemara (חגיגה טו:א) explains why not to look at the rainbow, amongst two other things that a person shouldn’t look at for a prolonged time – the Kohanim when they bless Klal Yisrael and at a Nasi. The Gemara explains that these things represent the Shechina; therefore, one shouldn’t look at them.

Go back to Parshas Noach