Psalm 110:4-6

Psalm 110:4-6 is also Trinitarian (and messianic, though it has yet to be fulfilled):

4. The LORD [God the Father] has sworn and will not change His mind: "You [God the Son] are a Priest forever like Melchizedek."

Christian scholars believe that Psalm 110 is messianic, for David prophesizes that the messiah will be the eternal priest / king (verse 4). This is fulfilled in the NT, as God the Son after his death and resurrection indeed became a king priest in the order of Melchizedek (Hebrews 5:6).

Here are two key messianic takeaways from verse 4:

- David’s master, God the Son, is a priest forever

- David was not a priest and was not even allowed to build the Temple (so how could the Messiah be David’s son?)

The mentions of three persons – e.g., “the Spirit was the witness to a conversation between David’s Lord, the Father and Son” – make it undeniably Trinitarian.

5. The Lord [God the Holy Spirit] is at Your [God the Son] right hand; He [God the Holy Spirit] will shatter kings in the day of His wrath.

If we read Psalm 110 carefully, we will notice that in verse 1, God the Father asks God the Son to sit at His right (So God the Father is at the Son’s left-hand side). Then, we read in verse 5: The Lord [God the Holy Spirit] is at Your [God the Son] right hand. Thus, we see there are two different Lords who are helping God the Son to claim his kingly priesthood.