And God said unto Noah, {m} This is the token of the covenant, which I have established between me and all flesh that is upon the earth.

(m) God repeats this often to confirm Noah's faith even more.

Matthew Henry's Concise Commentary

9:8-17 As the old world was ruined, to be a monument of justice, so this world remains to this day a monument of mercy. But sin, that drowned the old world, will burn this. Articles of agreement among men are sealed, that what is promised may be the more solemn, and the doing of what is covenanted the more sure to mutual satisfaction. The seal of this covenant was the rainbow, which, it is likely, was seen in the clouds before, but was never a seal of the covenant till now it was made so. The rainbow appears when we have most reason to fear the rain prevailing; God then shows this seal of the promise, that it shall not prevail. The thicker the cloud, the brighter the bow in the cloud. Thus, as threatening afflictions abound, encouraging consolations much more abound. The rainbow is the reflection of the beams of the sun shining upon or through the drops of rain: all the glory of the seals of the covenant are derived from Christ, the Sun of righteousness. And he will shed a glory on the tears of his saints. A bow speaks terror, but this has neither string nor arrow; and a bow alone will do little hurt. It is a bow, but it is directed upward, not toward the earth; for the seals of the covenant were intended to comfort, not to terrify. As God looks upon the bow, that he may remember the covenant, so should we, that we may be mindful of the covenant with faith and thankfulness. Without revelation this gracious assurance could not be known; and without faith it can be of no use to us; and thus it is as to the still greater dangers to which all are exposed, and as to the new covenant with its blessings.