Genesis 1:28-31 meaning

God said to them, "Be fruitful and multiply" (v 28). Regarding children, one of King David's psalms celebrates them as a great blessing.

Behold, children are a gift of the LORD, The fruit of the womb is a reward. Like arrows in the hand of a warrior, So are the children of one's youth. How blessed is the man whose quiver is full of them; They will not be ashamed When they speak with their enemies in the gate
(Psalm 127:3-5).

God tells the man and woman to subdue the earth, to conquer it or bring it into subjection. He gives them the right to rule over every living thing (v 28). This means they have the authority to take control, have power over, and dominate the earth. God commissions them to utilize the resources of the earth and be in charge over it. In verse 29, God gives the gift of plants and fruit from trees for food to sustain them and he gives plants to the animals for food.

This is quite amazing to reflect upon. God, who is all-powerful, handed over the rule of the earth to a newly created being. No wonder the Psalmist exclaims:

"What is man that You take thought of him,
And the son of man that You care for him?
Yet You have made him a little lower than God,
And You crown him with glory and majesty!
You make him to rule over the works of Your hands;
You have put all things under his feet"
(Psalm 8:4-6).

God chose humanity over the angels to rule the world. Why? Psalm 8 offers an explanation:

"From the mouth of infants and nursing babes 
You have established strength Because of Your adversaries,
To make the enemy and the revengeful cease"
(Psalm 8:2).

God chose "infants and nursing babes" - these newly arrived humans - over the mighty angels who had been in His presence to rule the earth. Hebrews 2:6-8 quotes Psalm 8 then, in what could be the greatest understatement in the Bible, observing, "But now we do not yet see all things subjected to him" (mankind). At this point in Genesis, mankind ruled the earth. But, because of the failings of mankind we do not presently possess that same authority over the world.

Hebrews 2 goes on to state that while we do not see humanity taking its proper place to rule over the earth with great stewardship and in perfect harmony with one another and with God, we do see something else quite extraordinary: 

"But we do see Him who was made for a little while lower than the angels, namely, Jesus, because of the suffering of death crowned with glory and honor, so that by the grace of God He might taste death for everyone.

For it was fitting for Him, for whom are all things, and through whom are all things, in bringing many sons to glory, to perfect the author of their salvation through sufferings"
(Hebrews 2:9-10).

This launches a grand drama in which humanity is a central actor, along with the angels and God Himself. Many modern stories revolve around the question "Who will rule the world?" This often involves fantasies about creatures from other places. We are a part of this kind of real drama. Which involves God (Jesus) who came in the form of a man in order to redeem humanity to its proper place in the world. 

God saw all that He had made and it was very good (v 31). Not just good, but abundantly, exceedingly good. God will redeem humanity to its proper place, for that is what God desired.

"For everything created by God is good"
(1 Timothy 4:4a).

This brings to a close the sixth day of creation.