He proves that Christ is called Lord of Hosts
Trypho: Let these things be so as you say—namely, that it was foretold Christ would suffer, and be called a stone; and after His first appearance, in which it had been announced He would suffer, would come in glory, and be Judge finally of all, and eternal King and Priest. Now show if this man be He of whom these prophecies were made.
Justin: As you wish, Trypho, I shall come to these proofs which you seek in the fitting place; but now you will permit me first to recount the prophecies, which I wish to do in order to prove that Christ is called both God and Lord of hosts, and Jacob, in parable by the Holy Spirit; and your interpreters, as God says, are foolish, since they say that reference is made to Solomon and not to Christ, when he bore the ark of testimony into the temple which he built. The Psalm of David is this:
The earth is the Lord's, and the fullness thereof; the world, and all that dwell therein. He has rounded it upon the seas, and prepared it upon the floods. Who shall ascend into the hill of the Lord? Or who shall stand in His holy place? He that is clean of hands and pure of heart: who has not received his soul in vain, and has not sworn guilefully to his neighbour: he shall receive blessing from the Lord, and mercy from God his Saviour. This is the generation of them that seek the Lord, that seek the face of the God of Jacob. Lift up your gates, you rulers; and be lifted up, you everlasting doors; and the King of glory shall come in. Who is this King of glory? The Lord strong and mighty in battle. Lift up your gates, you rulers; and be lifted up, you everlasting doors; and the King of glory shall come in. Who is this King of glory? The Lord of hosts, He is the King of glory.
Accordingly, it is shown that Solomon is not the Lord of hosts; but when our Christ rose from the dead and ascended to heaven, the rulers in heaven, under appointment of God, are commanded to open the gates of heaven, that He who is King of glory may enter in, and having ascended, may sit on the right hand of the Father until He make the enemies His footstool, as has been made manifest by another Psalm. For when the rulers of heaven saw Him of uncomely and dishonoured appearance, and inglorious, not recognising Him, they inquired, 'Who is this King of glory?' And the Holy Spirit, either from the person of His Father, or from His own person, answers them, 'The Lord of hosts, He is this King of glory.' For every one will confess that not one of those who presided over the gates of the temple at Jerusalem would venture to say concerning Solomon, though he was so glorious a king, or concerning the ark of testimony, 'Who is this King of glory?'
Source: Dialogue with Trypho (New Advent)