The Messiah would be called God's Son
Psalm 2 speaks of the nations of the world plotting against both God himself and his “Anointed.” Originally, this referred to the Davidic king, but the scope of what is described here, as well as later Jewish tradition, understood this to be referring to the Messiah, God’s Ultimate “Anointed.”
In verse 7, God specifically calls the Anointed “my Son” and promises worldwide rule in the face of the laughable opposition of the nations who counsel rebellion against God. Verse 12 is sometimes translated, “Do homage in purity,” or something similar, especially since the word in that verse for “son” is not the Hebrew ben as in verse 7, but the Aramaic bar, which seems out of place. Therefore, some have looked for an alternate translation. However, the switch to bar can be because (1) the psalmist is addressing the nations of the world, for whom Aramaic was the common language; and (2) otherwise, the Hebrew would have an odd-sounding phrase, ben pen (“Son, lest”), here made better by having bar pen.
The New Testament refers in numerous places to the ideas in this psalm:
Jesus as God’s Son:
“This he [God] has fulfilled to us their children by raising Jesus, as also it is written in the second Psalm, ‘You are my Son, today I have begotten you.’”
– Acts 13:33
For to which of the angels did God ever say, “You are my Son, today I have begotten you”? Or again, “I will be to him a father, and he shall be to me a son”?
– Hebrews 1:5
So also Christ did not exalt himself to be made a high priest, but was appointed by him [God] who said to him, “You are my Son, today I have begotten you.”
– Hebrews 5:5
The opposition to God and His Messiah:
“… who through the mouth of our father David, your servant, said by the Holy Spirit, ‘Why did the Gentiles rage, and the peoples plot in vain? The kings of the earth set themselves, and the rulers were gathered together, against the Lord and against his Anointed’ – for truly in this city there were gathered together against your holy servant Jesus, whom you anointed, both Herod and Pontius Pilate, along with the Gentiles and the peoples of Israel, to do whatever your hand and your plan had predestined to take place.”
– Acts 4:25-28
In the Hebrew Bible, “son of God” is used about angels (Job 1:6), about the nation of Israel (Exodus 4:22-23), and about Israel’s king (2 Samuel 7:14). In the New Testament, when Jesus is called “Son of God” or “God’s Son,” it implies: (1) he is the Messianic king; (2) he has a personal intimacy with the Father, whom he addressed as Abba; (3) he obeyed the Father, and especially; (4) his sonship is unique, unlike any other. For example, Jesus regularly speaks of “your Father” and “my Father” – but never “our Father” (Matthew 6:9 refers to what the disciples as a group are meant to pray; Jesus does not include himself in that group).
In contrast to what is often thought, it is the title Son of Man which Jesus frequently uses for himself that implies his divinity. That title comes from Daniel 7:13, which speaks of a heavenly figure. The title Son of God rather points to Jesus as the unique Messianic king who enjoys a special intimacy with God the Father, whose life is characterized by obedience to God, and whose career was marked by opposition, exactly like the Son of Psalm 2.