What does Psalm 45:7 mean?

In celebration of a king's marriage (Psalm 45:1), the psalmist has offered extravagant compliments (Psalm 45:2–5). These have included the deliberately exaggerated poetry often used in songs. In the prior verse, however, the psalmist made what seemed like a direct reference to God (Psalm 45:6). Since this song depicts a king in the line of David, it serves as a prophetic message about the Messiah, Jesus Christ. However, its immediate context is a particular human king. Most likely, the prior statement used terminology applied to human rulers.

In this verse, the same is true. However, it is easier to see a dual purpose which describes both the psalmist's then-ruling king and the prophesied Messiah, Jesus. The Gospel accounts of the earthly life of Jesus clearly reveal His love of righteousness. He refused to yield to temptation (Matthew 4:1–11). He continually performed God's will (John 8:29). In Acts 10:38 Peter told the crowd gathered in Cornelius's house that Jesus "went about doing good." Jesus detested wickedness (John 5:14). After forgiving the woman caught in the act of adultery, He told her: "Go, and from now on sin no more" (John 8:11). When He saw moneychangers turn the temple into a den of thieves, He drove out "those who sold and those who bought in the temple, and he overturned the tables of the money-changers and the seats of those who sold pigeons" (Mark 11:15).

This passage mentions intense joy and "gladness." This, also, is related to marriage (Isaiah 61:3)

According to Psalm 45:7, God has anointed His Son with the oil of gladness beyond His companions. The anointing with oil was part of Hebrew marriage proceedings and represents joy (Isaiah 61:3). Jesus' initial work as Messiah involved humility and even death (Isaiah 53:3–5; John 18:36; Philippians 2:5–8). His final works, however, will be to establish victory and eternal joy for His people (Philippians 2:9–11; Revelation 19:11–15; 21:1–4).