We cannot separate turning from sin in repentance and coming to Christ in faith. They describe the same person in the same action, but from different perspectives. In one instance (repentance), the person is viewed in relation to sin; in the other (faith), the person is viewed in relation to the Lord Jesus.
When the gospel is proclaimed, it seems at first sight that two different, even alternative, responses are called for. Sometimes the summons is, “Repent!” Thus, “John the Baptist came preaching in the wilderness of Judea, ‘Repent for the kingdom of heaven is at hand’” (Matt. 3:1–2). Again, Peter urged the hearers whose consciences had been ripped open on the day of Pentecost, “Repent and be baptized every one of you in the name of Jesus Christ” (Acts 2:38). Later, Paul urged the Athenians to “repent” in response to the message of the risen Christ (Acts 17:30).
Yet, on other occasions, the appropriate response to the gospel is, “Believe!” When the Philippian jailer asked Paul what he must do to be saved, the Apostle told him, “Believe in the Lord Jesus, and you will be saved” (Acts 16:31).
But there is no mystery or contradiction here. Further on in Acts 17, we discover that precisely where the response of repentance was required, those who were converted are described as believing (Acts 17:30, 34).
Any confusion is surely resolved by the fact that when Jesus preached “the gospel of God” in Galilee, He urged His hearers, “The time is fulfilled, and the kingdom of God is at hand; repent and believe in the gospel” (Mark 1:14–15). Here repentance and faith belong together. They denote two aspects in conversion that are equally essential to it. Thus, either term implies the presence of the other because each reality (repentance or faith) is the sine qua non of the other.
In grammatical terms, then, the words repent and believe both function as a synecdoche—the figure of speech in which a part is used for the whole. Thus, repentance implies faith and faith implies repentance. One cannot exist without the other.
But which comes first, logically? Is it repentance? Is it faith? Or does neither have an absolute priority? There has been prolonged debates in Reformed thought about this. Each of three possible answers has had advocates:
First, W. G. T. Shedd insisted that faith must precede repentance in the order of nature: “Though faith and repentance are inseparable and simultaneous, yet in the order of nature, faith precedes repentance” (Dogmatic Theology, 2.536). Shedd argued this on the grounds that the motivating power for repentance lies in faith’s grasp of the mercy of God. If repentance were to precede faith, both repentance and faith would be legal in character, and they would become prerequisites for grace.
Second, Louis Berkhof appears to have taken the reverse position: “There is no doubt that, logically, repentance and the knowledge of sin precede the faith that yields to Christ in trusting love” (Systematic Theology, p. 492).