By dying on the cross under the wrath of God that we deserve, Christ atoned for the sins of His people (Isa. 53). Note the qualifier “His people” in that sentence. When we discuss the atonement, it is insufficient to talk about it in general terms. Since penal substitution involves the one person, Jesus Christ, dying in place of others, we need to understand who those others are. Christ died intending to save people, but whom did He intend to save?
Most professing Christians would probably say that Jesus died for everyone in the world without exception. Yet, a careful reading of Scripture shows us otherwise. Christ, in fact, atoned only for the sins of His people, not the sins of every person who has ever lived.
John 10 is a key passage on this subject. Jesus says in verse 11 that He lays down His life for His sheep. If our Savior did atone for the sins of all people without exception, then everyone who has ever lived would have to be His sheep. Yet just a few verses later, Jesus makes reference to those who are “not among [His] sheep” (v. 26). It turns out that there is a difference between two groups of people that is significant to our discussion. Some people are the sheep of Jesus and some are not His sheep. But our Lord does not claim that He died for those who are not His sheep; rather, He died for His sheep alone.
In addition to the biblical evidence for Christ’s dying only for His elect, there are also important logical considerations. Christ in the atonement bears the punishment for sinners, so God would be unjust to punish in hell anyone for whom Christ died. If Christ bore the punishment for all sinners without exception, then either everyone who has ever lived must be in heaven or those who are in hell are being unjustly punished. (Their crime is being punished twice—once in Christ and once in them.) Yet we know that God is perfectly just and that some people go to hell (Deut. 32:4; Rev. 21:8). Christ, therefore, must have died only for those who are actually saved in the end.
Some have said that Christ died to save all people but that unbelief keeps some from receiving salvation. Yet, while we must believe in Jesus to be saved (Mark 16:16; Acts 16:31), unbelief is sin and is therefore also covered by the atonement. If Christ died for all unbelievers, we are back either to universalism or to God’s unjustly punishing sin twice. Thus, the only unbelief for which Jesus atoned is the unbelief of those who finally, by the work of the Spirit, abandon their unbelief and trust in Him alone for salvation.