A profitable and comforting word from the venerable William Gurnall speaking just to this matter:
II. SATAN EXAGGERATES THE SAINTS’ SINS
His [the devil's] aim is to discredit not the sins but the saints. Here his chief tactic is to deliver his accusations as if they are an act of the Holy Spirit. He knows a charge from God’s cannon wounds deeply; therefore, when he accuses a conscientious Christian, he forges God’s name on the missile before he fires it. Suppose a child were conscious of gravely displeasing his father, and some spiteful person, to harass him, wrote and sent him a counterfeit letter full of harsh and threatening accusations, copying the father’s name at the bottom. The poor child, already painfully aware of his sins and not knowing the scheme, would be overcome with grief. Here is real heartache stemming from a false premise – just the kind of thing Satan relishes.
Satan is a clever investigator. He closely observes the relationship between you and God. Sooner or later he will catch you tardy in some duty or faulty in a service. He knows you are conscious of your shortcomings and that the Spirit of God will also show distaste for them. So he draws up a lengthy indictment, raking up all the aggravations he can think of, then serves this warrant on you as though sent from God. This is how Job’s friends reacted to his trouble. They gathered up all the evidence of his infirmities to use against him, implying thy had been sent by God to declare him a hypocrite and denounce him for it.
While Satan is a master inquisitor, we know that not all our rebukes come from him. God’s Word clearly states that ‘Whom the Lord loveth he chasteneth’ (Heb 12:6). How, then, can we discern the spiteful accusations of Satan from the loving reprimands of God and His Spirit?
Try this test: If such rebukes contradict any prior work of the Spirit in your soul, they are Satan’s and not the Spirit’s. Satan’s purpose in emphasizing your sin is to try to unsaint you and persuade you that you are only a hypocrite. ‘Oh,’ hisses Satan, ‘now you have shown your true colors! See that horrid stain on your jacket – what other saint ever commited such a sin! Your whole life is a sham! God wants nothing to do with such a desperately wicked person as you.’
And with a single blow Satan dashes all in pieces. The whole mansion of grace which God has been building many years in our soul and all the special conmforts the Holy Spirit has brought are blown down by one gust from his malicious mouth. He leaves your life a shambles, and tells you it is your own fault.
Do not despair. Pacify your fears with this precious truth: Once the Spirit of God has begun a sanctifying work, causing you to hope in His mercy, He never will nor can bring contrary news to your soul. His language is not ‘yea and nay’, but ‘yea and amen’ for ever. If you play the prodigal, God will frown and chide you roundly for your sin, as He did David through Nathan: ‘Thou are the man!’ (2 Samuel. 12:7). Yet not a word is heard from Nathan telling David to unsaint himself and call in question the work of God in his soul. That prophet had no such commission form the Lord. He was sent to make David mourn for his sin – not from his sin to question his state of grace, which God had so often put beyond doubt.
Besides planting seeds of doubt about the sanctifying work of the Spirit, Satan often sends rebukes of the conscience that deny the riches of God’s grace. When you find your sins represented to you as exceeding either the mercy of God’s nature or the grace of His covenant, this comes from a jealous suitor, the devil. The Holy Spirit, as Christ’s intermediary, woos sinners to embrace the grace of the gospel. Would He say anything that would spoil the courtship or lower Christ’s esteem in the eyes of His beloved? Surely you must know where such lies orginate! When you hear someone compliment another person as wise or good, then at last come in with a but that dashes all, you know he is no friend but some sly enemy who, by seeming to commend the person, really desires to discredit him. And so, when you find God represented to you as merciful and gracious, but not to such a great sinner as you; strong and mighty, but not able to save someone like you, you can say, ‘Be gone, Satan, your speech betrays you. This is not a message sent to me by the Lover of my soul!’