From the fact that the Gentiles believe in Jesus, it is evident that He is Christ
And as they kept silence, I went on:
Justin: [The Scripture], speaking by David about this Christ, my friends, said no longer that 'in His seed' the nations should be blessed, but 'in Him.' So it is here: 'His name shall rise up for ever above the sun; and in Him shall all nations be blessed.' But if all nations are blessed in Christ, and we of all nations believe in Him, then He is indeed the Christ, and we are those blessed by Him. God formerly gave the sun as an object of worship, as it is written, but no one ever was seen to endure death on account of his faith in the sun; but for the name of Jesus you may see men of every nation who have endured and do endure all sufferings, rather than deny Him. For the word of His truth and wisdom is more ardent and more light-giving than the rays of the sun, and sinks down into the depths of heart and mind. Hence also the Scripture said, 'His name shall rise up above the sun.' And again, Zechariah says, 'His name is the East.' And speaking of the same, he says that 'each tribe shall mourn.' But if He so shone forth and was so mighty in His first advent (which was without honour and comeliness, and very contemptible), that in no nation He is unknown, and everywhere men have repented of the old wickedness in each nation's way of living, so that even demons were subject to His name, and all powers and kingdoms feared His name more than they feared all the dead, shall He not on His glorious advent destroy by all means all those who hated Him, and who unrighteously departed from Him, but give rest to His own, rewarding them with all they have looked for? To us, therefore, it has been granted to hear, and to understand, and to be saved by this Christ, and to recognise all the [truths revealed] by the Father. Wherefore He said to Him: 'It is a great thing for You to be called my servant, to raise up the tribes of Jacob, and turn again the dispersed of Israel. I have appointed You for a light to the Gentiles, that You may be their salvation unto the end of the earth.'
Source: Dialogue with Trypho (New Advent)