Repentance and Sorrow
The Greek word which is translated repentance implies a change of mind. Thus the child sent into the vineyard to work for his father said "I will not; but afterwards repenting himself he went" (Matt. 21: 29). In itself, repentance does not convey the thought of sorrow. This is very evident when the Lord speaks of the joy in heaven over one sinner that repents in the opening section of the parable of Luke 15 (see vs.1–10)—for with both the lost sheep and the lost coin there was clearly no sorrow. In the concluding section of the parable (see vs. 11–32), the prodigal son is described as coming to himself (see v17), and saying "I have sinned against heaven and before thee" (v21)—a process of soul which we would call repentance, although the word itself is omitted. However, we read nothing about sorrow, although it was surely present. The point is not so much that he was grieved by his wasted life, but that he had changed his mind about himself and about his father.
When the apostle Paul was preaching at Athens, he "reasoned ... in the synagogue with the Jews, and those who worshipped, and in the market–place" as well as on the Areopagus with "Epicurean and Stoic philosophers" (Acts 17: 17, 18). This was primarily an exercise in exhorting the Athenians to change their minds as to God and His Christ, and so the apostle preached that "God … now enjoins men that they shall all everywhere repent" (v30). He is not commanding men to sorrow but to change their minds—though if that change of mind is real, sorrow will accompany and result from it.
If repentance were simply sorrow for sin, how much would be sufficient? Surely no sorrow would be enough, and no mortal could ever give even a measure of what would be required. Indeed, what right has the sinner to define how much he ought to feel his sins? Thus while it is essential to see sorrow for sin, what God insists on above all is that definite and decided change of mind in His presence in which I take sides with God against myself—and which leads inevitably to placing faith in the Saviour He has provided. Thus, Paul speaks of his having testified "to both Jews and Greeks repentance towards God and faith towards our Lord Jesus Christ" (Acts 20: 21, my emphasis). Sorrow may and should accompany that repentance, and joy may and should accompany that faith, but sorrow is not repentance and joy is not faith.
It would be remiss of the writer, however, if he left the matter there. Certainly, there is a danger of mistaking feelings for faith, and grief for repentance, and it important to put a careful distinction between salvation and the emotions that ought to accompany it. Those, for example, that heard the word and immediately received it with joy were sadly afterwards found to have no root in themselves (see Matt. 13: 20, 21). There is an opposite peril, however, and that is of a merely intellectual assent to the truth. How sad it is to see numbers of professing Christians whose knowledge of the terms of the Gospel cannot be faulted, and yet who will one day, if they remain as they are, here those awful words "I never knew you" (Matt. 7: 23). Religion they may well have in ample quantities, but of Christ personally they have nothing. The test, as always, is "lovest thou me?" (John 21: 16). The testimony of Scripture is that "with [the] heart is believed to righteousness" (Rom. 10: 10, my emphasis). If the mind must be persuaded, so the heart must also be affected. A cold, intellectual belief is just as worthless as one built on frothy emotion.