Psalm 110:1-4 in Hebrews 7
¡1 (NIV) The LORD says to my Lord: "Sit at my right hand until I make your enemies a footstool for your feet." 2 The LORD will extend your mighty scepter from Zion; you will rule in the midst of your enemies. 3 Your troops will be willing on your day of battle. Arrayed in holy majesty, from the womb of the dawn you will receive the dew of your youth. 4 The LORD has sworn and will not change his mind: "You are a priest forever, in the order of Melchizedek."
¡Author is arguing that Jesus is the predicted king-forever.