Rom 12:9 . . . Abhor that which is evil; cleave to that which is good.
Our old nature is just the opposite of this. We love evil and despise that which is good. So, this is utterly impossible for an unbeliever. A believer is two different men, and we are instructed to put off the old man and to put on the new man, which after God is created in righteousness and true holiness (Eph 4:24). Only by obeying this can we obey our text.
The religious person who denies the existence of the new nature is self-righteous in attributing spiritual perception and ability to the old nature which it simply cannot possess. The only scriptural, God-honouring, flesh abasing way to account for this sin loving, good hater, to love good and hate evil, is the very nature and power of Christ that indwells the child of God. That new man is Christ in us (Jn 17:23), His very Spirit, dwelling in us (Rom 8), which is that new heart that He gives us (Ez 36:26).
I know that those who deny the new nature in the believer accuse us of self-righteousness, but there can be no greater or more obvious example of the pot calling the kettle black. What could be more self-righteous than any sinner claiming that they, with but their old nature, have the ability, to love God, hate evil, worship God, believe God and serve God? That which is born of the flesh, is flesh, will always be flesh and nothing but flesh, but bless God we are born from above, new creatures in Christ Jesus. Not improved creatures, but new ones . . .
What is evil and what is good? Well everyone knows that. No one knows this without being taught of God. Here is God’s indictment upon all of sinful mankind: Isaiah 5:20 Woe unto them that call evil good, and good evil; that put darkness for light, and light for darkness; that put bitter for sweet, and sweet for bitter! Religious man considers going to church a good work, but God said in Isaiah chapter one that man’s religious, solemn meetings are iniquity. Why? It is not the outward act that determines whether something is good or evil. If you attend worship services this morning in order to please God so He will deal favorably with you, then you are committing sin. Christ and Christ alone is our righteousness, favor with God, and all blessing we have is because of Him. If we ever we feel we have earned God's favor with any act of ours, we trample underfoot the precious blood of Christ. If, on the other hand, you attend because you genuinely love Christ and want to hear His Gospel (Christ crucified) preached and fellowship with His people and truly worship Him, then you are blessed of God. You have, by His grace, chosen that good part (Luke 10:42).
Most would consider prayer good, but just the act of praying itself is not necessarily so. God told the Christless religionist in Isaiah 1:15, “I will not hear.” That which glorifies God in all of His Persons, is good, and that which glorifies man, such as fleshly, man-centered, free-will religion, is evil. May God give us grace to abhor the evil, and cleave to that which is good.