Question: Going back to the subject of men not eating meat before the Flood: When God spoke to Noah after the Flood, in Genesis 9:3, he said, "Everything that lives and moves about will be food for you. Just as I gave you the green plants, I now give you everything." Wasn’t God referring to Genesis 1:29 which says, "I give you every seed-bearing plant on the face of the whole earth and every tree that has fruit with seed in it. They will be yours for food"? So men didn’t eat meat until after the Flood when God gave them permission to eat meat.
Answer: Yes we can go back to this subject. I have spoken about it before on "Were People Vegetarians."
God told Noah to “bring into the ark two of all living creatures, male and female, to keep them alive with you” (Gen 6:19). On the ark Noah and his family didn’t kill any animals to eat because they were told to “keep them alive.” While Noah was on the ark there was a restriction about killing animals. Noah's cargo of pairs of animal species was not for eating but for preserving. Once the Flood was over, that restriction no longer applied because the animals would breed. In Genesis 9:3 God tells Noah that he is no longer obliged to keep the animals alive but may now kill them and eat the meat.
So Genesis 9:3 (“Just as I gave you the green plants”) does not refer back to Genesis 1:29 but to Genesis 6:19–21 where Noah is told to “take every kind of food that is to be eaten and store it away as food for you and for them (Gen 6:21). "Take with you seven pairs of every kind of clean animal" (Gen 7:2). That is a lot of animals to feed for a year. God provided this food by giving to Noah the green plants.
Furthermore, if we look closely at the phrase spoken by God to Noah in Genesis 9:3, “Just as I gave you the green plants,” we can see two points that may be useful.
Firstly, God didn’t say he gave “green plants” to humankind in Genesis chapter 1: he gave the “green plants” to the beasts - "to all the beasts of the earth and all the birds in the sky and all the creatures that move along the ground—everything that has the breath of life in it—I give every green plant for food” (Gen 1:30). To humans he gave “every seed-bearing plant on the face of the whole earth and every tree that has fruit with seed in it” (Gen 1:29).
Secondly, let’s remember that God is speaking to Noah here, in Genesis 9:3, and he is referencing having spoken to Noah before, saying, “Just as I gave you the green plants.” This allows us to see that at some point previously God had spoken to Noah about the green plants. The green plants were given to Noah to feed his animals while they were on the ark. Green plants (i.e., fodder, grass, leaves, etc.) were given to the animals to eat; they were not given to humans; we can’t eat grass very well. The clean animals that Noah carried on the ark would have normally eaten a grazing diet, what we term as grass-fed; they would belong to a pasture-raised herd or flock, others would be browsers; these animals eat a variety of plant material including leaves. (The unclean animals, predators, on board the ark would have eaten smaller creatures that Noah would also have a stock of on board the ark.)
Noah needed to provide enough fodder for the animals and food for the humans on board the ark, so God made sure the supply of vegetation around the dry Mesopotamian landscape was sufficient for Noah to harvest and take on board the ark.
There needed to be over one year’s supply, so God gave Noah a bumper harvest of “green plants” as a special provision for the duration they would be needed on the ark to feed the clean animals, such as cattle, sheep, and goats, of which there were seven pairs each: "Take with you seven pairs of every kind of clean animal" (Gen 7:2). So that's a fair amount of fodder needed.
There is no command telling people to refrain from eating meat in the first chapter of Genesis.