The Noachian Covenant
When Noah and his family disembarked from the ark, releasing the animals, God evidently de-pacified the animals (as they had apparently been made docile by Him for their voyage on the ark). At this point He also delegated the administration of the death penalty to man. At the same time God permitted meat to be eaten (verse 3).
Some seize on this as proof that men were supposed to be vegetarians before the Flood. However, Abel sacrificed an animal and, as Leviticus shows, parts of sacrifices were eaten. Moreover, the apostle Paul later explained that some animals—those the Bible designates as “clean” (see Leviticus 11; Deuteronomy 14)—were created to be eaten (1 Timothy 4:3-4 1 Timothy 4:3-4  Forbidding to marry, and commanding to abstain from meats, which God has created to be received with thanksgiving of them which believe and know the truth.
 For every creature of God is good, and nothing to be refused, if it be received with thanksgiving:
American King James Version×). Indeed, we already saw the distinction drawn between clean and unclean—i.e., edible and inedible—animals before the Flood in Genesis 7. Why would there have been a distinction at that time if animals were not then eaten? Thus it appears that God was simply telling Noah and his family that it was okay to eat animals again—which likely means they had not been permitted to kill any of the live animals on the ark in order to have eaten them while still aboard. Perhaps that would have depleted some species before they had a chance to amply multiply after the Flood.
God also established a special covenant with man, promising never to send a universal deluge again. As a token (or sign) of the promise, God “set” the rainbow in the sky (verse 13). The Hebrew word translated “set” is nathan, meaning give. This has led some to suggest that the rainbow had never been seen before. If this suggestion is true, it would mean that God either modified the laws of physics governing optics, for a rainbow is just the product of the refraction of light through the medium of airborne water droplets, or that He altered the atmosphere of the earth, perhaps by removing some kind of upper vapor canopy that formerly altered the character of the light reaching the earth’s surface. Such a vapor canopy may help to explain the rain of 40 days and 40 nights when the “windows of heaven were opened” (Genesis 7:11-12 Genesis 7:11-12  In the six hundredth year of Noah's life, in the second month, the seventeenth day of the month, the same day were all the fountains of the great deep broken up, and the windows of heaven were opened.
 And the rain was on the earth forty days and forty nights.
American King James Version×). And this may have constituted the “waters which were above the firmament” in Genesis 1:7 Genesis 1:7And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so.
American King James Version×.
A Curse on Canaan
Some decades after the Flood (time enough for Noah’s sons to father their own sons and for these grandchildren to grow up), Noah became a husbandman, growing grapes and making wine. Then, when he drank the wine, he became intoxicated and fell asleep in his tent, whereupon, the Bible records, his nakedness was uncovered. This expression is used throughout Leviticus 18 to denote sexual relations. When Noah’s son Ham discovered him, he told his brothers, who then covered their father. When Noah awoke, he learned of what happened and called forth a curse upon Ham’s youngest son, Canaan. Why? Why should Canaan be cursed?
Verse 24 states that Noah “knew what his younger son had done to him.” This is often interpreted to mean that Noah “knew what his [Noah’s] younger son [Ham] had done to him.” Yet if Ham himself were guilty of whatever wrong had been committed, we might assume that Noah would have cursed him personally or, if his offspring were to be cursed, that it would apply to all his offspring or perhaps the eldest and his family rather than just Ham’s youngest son Canaan and those who would spring from him. So the most likely scenario is that Canaan himself had committed the wrong—apparently some sexual sin against Noah while Noah was intoxicated—which Ham discovered. Thus verse 24 should probably be understood to read that Noah “knew what his [Ham’s] younger son [Canaan] had done to him”—particularly if we consider verse 23 as parenthetical.