Charles H. Spurgeon on Psalms 18:45

"The strangers shall fade away." Like sear leaves or blasted trees our foes and Christ's foes shall find no sap and stamina remaining in them. Those who are strangers to Jesus are strangers to all lasting happiness; those must soon fade who refuse to be watered from the river of life. "And be afraid out of their close places." Out of their mountain fastnesses the heathen crept in fear to own allegiance to Israel's king, and even so, from the castles of self-confidence and the dens of carnal security, poor sinners come bending before the Saviour, Christ the Lord. Our sins which have entrenched themselves in our flesh and blood as in impregnable forts, shall yet be driven forth by the sanctifying energy of the Holy Spirit, and we shall serve the Lord in singleness of heart.

Thus with remembrance of conquests in the past, and with glad anticipations of victories yet to come, the sweet singer closes the description, and returns to exercise of more direct adoration of his gracious God.