Here, in verse 4, the psalmist takes an important Old Testament ruler called Melchizedek and says that his story is a picture of Jesus. Melchizedek was a king in Salem (which may have been an old name for Jerusalem) who also functioned as the priest in his community. Unlike the Jewish priests, he was also a king and so depicts Jesus who is both a king and a priest.
The Book of Hebrews develops this reference to Melchizedek, especially the lack of a genealogy for him and also the meanings of his name. Usually in Genesis, we are told when a person was born and when he died. The omission of this detail about Melchizedek makes him a picture of the eternal person of the Son of God, who had no beginning and will have no end. Of course, Melchizedek was born and died because he was only a man. Some have speculated whether he was Jesus making an Old Testament appearance, but that is wrong.
With regard to his name, he also illustrates who Jesus is and what he did. His name means ‘king of righteousness’ and his location Salem means he was also king of ‘peace’. Jesus provides both of these blessings for his subjects. Sin had deprived us of both these blessings, but Jesus restores us to a standing marked by both. He has provided a permanent righteousness for those who trust in him and his work on the cross also has made permanent peace between them and God.
When Melchizedek met with Abraham, he brought physical refreshment to the tired patriarch who was returning from a battle in which he had rescued his nephew Lot. In this activity, Melchizedek is also a picture of Jesus who provides spiritual refreshment for his people throughout their time in this world. They will face many difficult situations, but he always knows how to draw near and help them.
On that occasion back in Genesis, Abraham acknowledged the supremacy of Melchizedek by giving to him a tithe. This action by Abraham illustrates that we should acknowledge the pre-eminence of Jesus by gladly giving to him what he commands from us.
The psalmist is aware of an incident that would yet occur in heaven from his perspective. It was revealed to him that the Messiah would yet be invited to take his place on the throne of God, and that the invitation would include this reference to Melchizedek. So even in heaven, when announcements are made, some of them at least refer to incidents recorded in the Word of God. Perhaps people may have wondered what significance there was in referring to this otherwise unknown figure. The reference in Psalm 110 explains his importance. It may be the case that other announcements in heaven will yet highlight the deeper meaning of many biblical passages that currently seem to have little to say.