If thou pretendest now to be a child of God, and if thou hast never clothed thyself in dust and ashes; if thou hast never hated the sins which once thou didst love: if thou dost not now hate them, and endeavor to be rid of them, if thou dost not humble thyself before God on account of them, as the Lord liveth, thou knowest nothing about saving faith, for faith puts a distance between us and sin; in a moment it leads us away from the distance between us and Christ; nearer to Christ, we are now far off from sin. But he that loves his sin, thinks little of his sin, goes into it with levity, talks of it sportively, speaks of sin as though it were a trifle, hath the faith of devils, but the faith of God’s elect he never knew. True faith purges the soul, since the man now hunts after sin that he might find out the traitor that lurks within his nature; and though a believer is not perfect, yet the drift of faith is to make him perfect; and if it is faith to be perfected, the believer shall be perfected, and then shall he be caught up to dwell before the throne. Judge yourselves, my hearers. Have you brought forth the fruits of repentance? If not, your faith without them is dead.
— Rev. C.H. Spurgeon, The Treasure of Grace, 1860
Examine yourselves, to see whether you are in the faith. Test yourselves. Or do you not realize this about yourselves, that Jesus Christ is in you?—unless indeed you fail to meet the test!
2 Corinthians 13:5 (ESV)