Psalm 110 Mar. 5 A Psalm by David.  1Yahweh says to my Lord, Sit at My right hand, until I make your enemies a footstool for your feet. 2Yahweh will send forth the rod of your strength out of Zion. Rule in the midst of your enemies! 3Your people offer themselves willingly in the day of your power, in holy attire. Out of the womb of the morning, you have the dew of your youth. 4Yahweh has sworn, and will not change His mind: You are a priest forever in the order of Melchizedek. 5The Lord is at your right hand; He will crush kings in the day of His wrath. 6He will judge among the nations, He will heap up dead bodies, He will crush the ruler of the whole earth. 7He will drink of the brook in the way; therefore He will lift up His head.   

Commentary

110:1 This verse is quoted in Mt. 22:44 and Acts 2:34,35 with the understanding that David’s “lord” or master was Jesus, who was bidden sit in Heaven at His right hand after His resurrection, declared a priest for us in the order of Melchizedek, until He returns to earth to be King in Jerusalem (“Zion”) and destroy all God’s enemies. 
110:2 Rule in the midst of your enemies- This supports the impression we get from Psalm 2, that when Christ returns He will establish His Kingdom but there will initially be opposition to Him, and the nations will gather together against Him, surrounding Jerusalem (cp. Rev. 20:9). It’s amazing how much humanity wants to carry on as it is, with all their religions, and not be disturbed by the intervention of God in their lives. And this feature of our world will be revealed in their attitudes to Christ at His return.
110:3 The exhortation of Ps. 110 is powerful: because Jesus is now seated at the Father's right hand, His people offer themselves as freewill offerings in this, the day of His power. They are arrayed in "holy attire" because He has been made the Priest after the order of Melchizedek- they share in the work which His exaltation has enabled.
110:4 This is repeatedly applied to Christ (Heb. 5:6,10; 6:20; 7:11,17,21). The priests were from the tribe of Levi, whereas Christ was from Judah. Melchizedek was king of Jerusalem and yet also a priest; but he wasn’t a Levite. He is therefore chosen as an appropriate type of Christ, the ultimate king-priest. This argument is deployed in Hebrews to answer the Jewish objection that Christ can’t be a priest because He wasn’t a Levite.