Unto me, who am less than the least of all saints, is this grace given, that I should preach among the Gentiles the unsearchable riches of Christ… – Ephesians 3:8

(One) reason why the Lord takes the vilest of men to make them the saintliest is, that He might openly triumph over Satan. How the devil must feel defeated when such a man as Saul is taken straight away from persecuting to preaching! Surely, it makes Satan bite his chains and gnash his teeth when he loses his servants so. Just when he has trained them up, and got them into fine condition for doing mischief, in comes the officer of divine grace, arrests them, and changes their hearts. You know none ever do the devil so much mischief as those who once did him service…All heaven rings with rapture when a great sinner is saved; and all hell howls with dismay when one of the arch host bows down to kiss the feet of Christ and receive the mercy of God. Glory be to God when He takes those that would have been deepest damned and sets them highest among the saved on earth to be priests and Levites unto Him. By these means also He secures another end: He encourages poor penitents; for when a sinner, under a sense of sin, meets with a brother in Christ, who was like himself once, but is now living near to God and serving Him acceptably, he is much encouraged. “Why,” he thinks to himself, “is this how God receives sinners when they turn to Him? Perhaps He will receive me.” And if he gets into conversation with one of those whom God has made priests and Levites, he says, “Tell me what the Lord has done for thy soul.” And the minister being a man of like passions, and having had like experience, delights to describe the works and ways of God with hardened sinners and old offenders and then the man who is seeking finds in the other a guide who is touched with the feeling of his infirmity, is very helpful to him, and much blessed of God to enter into the secrets of his heart and lead him to the cross. If there be here some great rebel against God, I think he ought to take encouragement thence to turn unto the Lord and live, for surely, when God so treats His most defiant enemies as to make them His most honored ministers, there should be some comfort for the great sinner to seek the Lord while yet He waits to be gracious. ~ C.H. Spurgeon

https://www.blueletterbible.org/comm/spurgeon_charles/sermons/0992.cfm