John 16:33 (ESV) … “I have said these things to you, that in me you may have peace. In the world you will have tribulation. But take heart; I have overcome the world.”
Jesus overcame the prince of this world (Satan) by his death, Jn. 12:31. Jesus vanquished the great foe of man, and triumphed over all that would work our ruin. He brought down aid and strength from above by his death; and by procuring for us the friendship of God and the influence of the Spirit; by his own instructions and example; by revealing to us the glories of heaven, and opening our eyes to see the excellence of heavenly things, he has furnished us with the means of overcoming all our enemies, and of triumphing in all our temptations.
Luther said of this verse “that it was worthy to be carried from Rome to Jerusalem upon one’s knees.” The world is a vanquished enemy; Satan is a humbled foe; and all that believers have to do is to put their trust in the Captain of their salvation, putting on the whole armor of God, assured that the victory is theirs, and that the church shall yet shine forth fair as the moon, clear as the sun, and terrible as an army with banners, Song of Solomon 6:10 “Who is this who looks down like the dawn, beautiful as the moon, bright as the sun, awesome as an army with banners?” [1]
[1] Barnes, A. (1884–1885). Notes on the New Testament: Luke & John. (R. Frew, Ed.) (p. 352). London: Blackie & Son.