1. Psalm 8 might be categorized as a psalm of thanksgiving or perhaps a psalm of praise. It marvels at what a privileged place God has assigned to humanity in relation to the creation. It was a key psalm for the New Testament as well.
2. The psalm begins by praising God for his majesty, for his glory above the heavens. This praise comes even from the mouths of babes (8:2). What a magnificent work he has done in creation! All we need do is look at the heavens.
3. Over and against God's greatness, there is the marvel that he would care so much for insignificant humanity. What is it about us that God would put us in authority over the other creatures of his creation? God has put everything under humanity's feet--sheep, oxen, the beasts of the field, the birds of the air, the fish of the sea.
The psalm ends as it began (an "inclusio"): "O LORD, our Lord, how majestic is your name in all the earth (8:9). Two words are used here. LORD in all capital letters is the name of God, YHWH. Then "Lord" is Adonai, a master.
4. "You made him a little less than God" (8:5). The word here is 'elohim, a word normally translated "God." The Greek OT translated it as "angels," and this is the form in which the NT translates it. But "God" is the default translation in the OT. It is possible of course that it is a genuine plural--you have made humanity a little lower than gods (cf. Ps. 82). The ESV, perhaps wearing its theology on its sleave, translates it as "heavenly beings."
5. Psalm 8 was a key text for the earliest Christians. They joined it with Psalm 110:1 and read it in relation to Christ, the one in regard to whom "God put all things under his feet" (cf. 1 Cor. 15:27). Hebrews 2 perhaps gives us the full expression of what the earliest Christians were thinking. God created humanity to have a position of glory and honor in the creation (Ps. 8:5).
But "all have sinned and are lacking the glory of God" (Rom. 3:23). This is the human situation: "We do not yet see everything in subjection to them" (Heb. 2:8).
Now Jesus enters into the equation. He enters into the human condition. "We do see Jesus who for a little while was made lower than the angels" (2:9). He has been crowned with glory and honor through his suffering of death. Now he can lead many sons and daughters to glory (2:10), to the glory God originally intended humanity to have.
Psalm 8 was thus the story of salvation in a nutshell for the author of Hebrews, who quite possibly is showing us the fuller theology of Paul lurking behind his allusive references to the psalm here and there in his writings.
2:16-19 warn against a married woman who might seduce a man. Of course this is a two way street. It seems likely that for most if not all of history, it is the married man who has seduced far more than the married woman. We should take these verses as a warning against the temptation to adultery in general.
2:20-22 expresses the way it should always work. The upright should inherit the land and the unrighteous should be rooted out of it. The whole of the canon makes it clear that such justice will not always take place while we are in this age or in this life. The NT has made it clear, though, that it will happen eternally.
Psalm 1 and Proverbs 1:1-7
Psalm 2 and Proverbs 1:8-14
Psalm 3 and Proverbs 1:15-19