The Moral & Immoral Both Alienated from God
Both moral and immoral individuals are alienated from God and are offensive to Him. This may be counterintuitive, but moral people may be lost due to their "goodness." Why? It is often the case that goodness keeps people from God. In fact, many people avoid sin and Jesus in an attempt to become their own saviors, justifying themselves. However, the gospel is not about moralism or relativism and is equally offensive to both the moral and the irreligious. Christ calls us to repent of both our good and bad works, for we have no righteousness of our own.
Jesus disapproved of people who trusted in their own morality, as shown by His statement, "If you were blind, you would have no guilt; but now that you say, 'We see,' your guilt remains" (John 9:41). Those who believe that God will accept them based on their goodness only understand part of the truth. Although God loves what is good, He also loves the truth. Therefore, we must confess that, in light of God's holy law, we are not good and have woefully failed to do what is pleasing to God, replacing Him with worthless self-pleasing idol substitutes, and deserve punishment for it. Those who think they have done enough to please God have not understood the seriousness of their condition. John Calvin once said, "Man is never sufficiently touched and affected by the awareness of his lowly state until he has compared himself with God's majesty." In light of God's holiness, all individuals, even the best of us, would become undone. This was even the case with the holiest saints of the Bible, who fell at God's feet as though dead when He revealed Himself to them. God created us to enjoy and glorify Him, but humans voluntarily rebelled against Him, falling into the bondage of the self-centeredness of sin, and cannot help themselves out of it.
For clarification, no one would dare to reason that we should be content to be immoral because we cannot trust in morality. Those who are regenerated by the Spirit of God will want to obey God, and His commands are not burdensome because such persons have been born of God (1 John 5:1-4). We obey because we are saved, not in order to be saved. To those who come to faith in Jesus by the quickening grace of the Spirit (John 6:63), the commands taste like honey, as we are no longer slaves but children. As Matthew Henry once said, "When the Law of God is written on our hearts, our duty will be our delight."
A Christian is not only someone who, by the grace of God, has repented of their immorality, but, even more importantly, has repented of their morality. The more self-righteous one is, the worse it is for them. Our own merits are of no value for salvation and will damn us. Whoever relies on their own goodness for salvation will suffer complete ruin.
[Some people being very moral have] "nothing to do with the business of repentance. They are so good, that they scorn God's offer of mercy. Indeed these are often in the worst condition: these are they who think they need no repentance (Luke 15:7). Their morality undoes them. They make a "savior" of it, and so on this rock they suffer shipwreck. Morality shoots short of heaven. It is only nature refined. A moral man is but old Adam dressed in fine clothes. The king's image counterfeited and stamped upon brass will not go current. The moral person seems to have the image of God—but he is only brass metal, which will never pass for current. Morality is insufficient for salvation. Though the life is moralized, the lust may be unmortified. The heart may be full of pride and atheism. Under the fair leaves of a tree, there may be a worm. I am not saying, repent that you are moral—but that you are no more than moral. Satan entered into the house that had just been swept and garnished (Luke 11:26). This is the emblem of a moral man, who is swept by civility and garnished with common gifts—but is not washed by true repentance. The unclean spirit enters into such a one. If morality were sufficient to salvation, Christ need not have died. The moral man has a fair lamp—but it lacks the oil of grace."
From Thomas Watson, The Doctrine of Repentance
[Some people end up] "Trusting in their own righteousness. This is a soul-ruining mischief. When men trust in their own righteousness they do indeed reject Christ's. Beloved, you had need be watchful on every hand, for not only your sins—but your duties may undo you. It may be you never thought of this; but so it is, that a man may as certainly perish by his seeming righteousness and supposed graces—as by gross sins; and that is, when a man trusts to these as his righteousness before God, for satisfying His justice, appeasing His wrath, procuring His favor, and obtaining His pardon. This is to put Christ out of office, and make a Savior of our own duties and graces. Beware of this, O professing Christians; you are much in duties—but this one fly will spoil all the ointment. When you have done most and best, be sure to go out of yourselves—to Christ; reckon your own righteousness as filthy rags (Phil 3:9; Isa 64:6)."
Joseph Alleine, A Sure Guide to Heaven