Articles of agreement among men are usually sealed, that the covenants may be the more solemn, and the performances of the covenants the more sure, to mutual satisfaction. God therefore, being willing more abundantly to show to the heirs of promise the immutability of his councils, has confirmed his covenant by a seal (Hebrews 6:17), which makes the foundations we build on stand sure, 2 Timothy 2:19.
The seal of this covenant of nature was natural enough; it was the rainbow, which, it is likely, was seen in the clouds before, when second causes concurred, but was never a seal of the covenant till now that it was made so by a divine institution.
Now, concerning this seal of the covenant, observe, 1. This seal is affixed with repeated assurances of the truth of that promise of which it was designed to be the ratification: I do set my bow in the cloud (Genesis 9:13); it shall be seen in the cloud (Genesis 9:14), that the eye may affect the heart and confirm the faith; and it shall be the token of the covenant (Genesis 9:12-13), and I will remember my covenant, that the waters shall no more become a flood, Genesis 9:15.
Nay, as if the Eternal Mind needed a memorandum, I will look upon it, that I may remember the everlasting covenant, Genesis 9:16. Thus here is line upon line, that we might have sure and strong consolation who have laid hold of this hope.
2. The rainbow appears when the clouds are most disposed to wet, and returns after the rain; when we have most reason to fear the rain prevailing, then God shows this seal of the promise that it shall not prevail.
Thus God obviates our fears with such encouragements as are both suitable and seasonable. 3. The thicker the cloud the brighter the bow in the cloud. Thus, as threatening afflictions abound, encouraging consolations much more abound, 2 Corinthians 1:5.
4. The rainbow appears when one part of the sky is clear, which intimates mercy remembered in the midst of wrath; and the clouds are hemmed as it were with the rainbow, that they may not overspread the heavens, for the bow is coloured rain or the edges of a cloud gilded.
5. The rainbow is the reflection of the beams of the sun, which intimates that all the glory and significancy of the seals of the covenant are derived from Christ the Sun of righteousness, who is also described with a rainbow about his throne (Revelation 4:3), and a rainbow upon his head (Revelation 10:1), which intimates, not only his majesty, but his mediatorship.
6. The rainbow has fiery colours in it, to signify that though God will not again drown the world, yet, when the mystery of God shall be finished, the world shall be consumed by fire. 7. A bow bespeaks terror, but this bow has neither string nor arrow, as the bow ordained against the persecutors has (Psalm 7:12-13), and a bow alone will do little execution.
It is a bow, but it is directed upwards, not towards the earth; for the seals of the covenant were intended to comfort, not to terrify. 8. As God looks upon the bow, that he may remember the covenant, so should we, that we also may be ever mindful of the covenant, with faith and thankfulness.