Tafsiran Kejadian 9:17: Rashi, Sforno & Radak

זאת אות הברית THIS IS THE SIGN OF THE COVENANT — He pointed to the rainbow, and said to him, “This is the sign of which I have spoken.”

ויאמר אלוקים לנח זאת אות הברית, the word זאת refers to the “secondary” rainbow, [I mentioned earlier. Ed.] which acts as the sign of the warning aspect of the covenant. When this rainbow appears it is high time to call people to order and to warn them of impending natural calamities unless they change their ways.

ויאמר אלוקים, G’d repeated His blessings a third time in order to reassure him beyond doubt. According to Bereshit Rabbah 38 our paragraph contains 6 covenants which were meant to correspond to the six days of the creation. If you were to question that actually there are 7, the answer is that the first one was needed in its own right, and cannot be used to relate to other matters. [what are meant by “6 covenants,” are the 6 (respectively 7) separate utterances reported by G’d in this paragraph, utterances which could have been considerably condensed by the use of longer sentences and conjunctive letters. Ed.]