After the great flood, Noah and his family honored God with a sacrifice. God was pleased and promised to never again destroy every living thing. The heart of humans are wicked and sinful, that is why we all need a Savior. The Old Testament prophesizes the coming of Jesus. Nobody is good enough, so God had to send his son to earth to redeem us of our sins.

God’s Covenant with Creation
Then Noah built an altar to the Lord, and took of every clean animal and of every clean bird, and offered burnt offerings on the altar. And the Lord smelled a soothing aroma. Then the Lord said in His heart, “I will never again curse the ground for man’s sake, although the imagination of man’s heart is evil from his youth; nor will I again destroy every living thing as I have done.“While the earth remains,
Seedtime and harvest,
Cold and heat,
Winter and summer,
And day and night
Shall not cease.”
—Genesis 8:20-22
God made a covenant between Noah and every living creature to never again destroy the earth with a flood, which can be seen as a rainbow. After rain, whenever we see a rainbow, it is a sign of the the everlasting covenant between God and every living creature of all flesh that is on the earth. I bolded the words rainbow and covenant phrases in the scripture verses below as a way to highlight these words.
God’s Promise to Noah
Then God spoke to Noah and to his sons with him, saying: And as for Me, behold, I establish My covenant with you and with your descendants after you, and with every living creature that is with you: the birds, the cattle, and every beast of the earth with you, of all that go out of the ark, every beast of the earth. Thus I establish My covenant with you: Never again shall all flesh be cut off by the waters of the flood; never again shall there be a flood to destroy the earth.”And God said: “This is the sign of the covenant which I make between Me and you, and every living creature that is with you, for perpetual generations: I set My rainbow in the cloud, and it shall be for the sign of the covenant between Me and the earth. It shall be, when I bring a cloud over the earth, that the rainbow shall be seen in the cloud; and I will remember My covenant which is between Me and you and every living creature of all flesh; the waters shall never again become a flood to destroy all flesh.The rainbow shall be in the cloud, and I will look on it to remember the everlasting covenant between God and every living creature of all flesh that is on the earth.” And God said to Noah, “This is the sign of the covenant which I have established between Me and all flesh that is on the earth.”
—Genesis 9:8-16