In 1 Corinthians 7:10, Paul writes: “But to the married I give instructions, not I, but the Lord, that the wife should not leave her husband.” But only two verses later in verse 12 he writes: “But to the rest I say, not the Lord, that if any brother has a wife who is an unbeliever, and she consents to live with him, he must not divorce her” (emphasis added).

What is going on here? Does Paul issue the Lord’s command in the first instance, but only offer a personal opinion in the second? Do we have to obey the first instruction but not the second since Paul says that the second comes from him rather than from the Lord?

New Testament scholars on the whole are in agreement that the distinction Paul is making here is not between his own personal opinion and God’s authoritative instruction; rather, he is contrasting the source of authority for each instruction. Both statements are fully authoritative, but the source of authority differs in each instance.

In the early second century, Polycarp of Smyrna, one of Christianity’s most famous martyrs, lists three sources of authority for early Christians. He writes, “So, then, let us serve him with fear and all reverence, just as he himself [Jesus] has commanded, as did the apostles, who preached the gospel to us, and the prophets, who announced in advance the coming of our Lord” (Pol. Phil. 6.3).

The three sources of authority for the earliest Christians were: (1) the teachings of Jesus passed on orally by the apostles; (2) the instructions of the apostles (cf. Acts 2:42); and (3) the words of the prophets, that is, the Old Testament Scriptures. These three streams of authority were different from each other stream, but each of the three was binding on early Christians.

So in 1 Corinthians 7, Paul distinguishes between source-of-authority No. 1 and source-of-authority No. 2. When Paul writes in 1 Corinthians 7:10, “not I, but the Lord,” he is appealing to the specific teaching Jesus gave about divorce when he was on earth.

Did Jesus give instructions during his earthly ministry that a wife should not leave her husband? Yes, the early disciples orally passed on Jesus’ prohibition of divorce until it was written down in the Gospels a decade or so after Paul wrote 1 Corinthians (cf. Mark 10:11-12; Matthew 19:6, 9).

So when Paul passes on the particular instruction found in 1 Corinthians 7:10, he wants to draw attention to the fact that this teaching is not new; it was given by the Lord himself some 20 years earlier. Paul’s appeal in this verse, then, is to source-of-authority No. 1, the specific teaching of Jesus in his earthly ministry as passed down orally by the early disciples and written down in this verse by Paul.

But did Jesus give instructions during his earthly ministry about what to do in the case of a believer who is already married to an unbelieving spouse? No, there is no evidence in any of the Gospels that Jesus ever had reason to teach about such a situation during his earthly ministry.

So Paul gives authoritative instructions as God’s appointed apostle about what to do in this particular situation. In this case, his appeal is to source-of-authority No. 2, the authority of the apostles (of which he is one). His instruction is still a “trustworthy” word of the Lord, even if Jesus didn’t teach about it during his earthly ministry (1 Corinthians 7:25), because, as Paul says about himself, “I also have the Spirit of God” (1 Corinthians 7:40). Paul is a divinely appointed apostle who has authority to give such directions to the churches (1 Corinthians 7:17).

So despite the common assumption that Paul is just giving his personal opinion in 1 Corinthians 7:12, there are good reasons — as a glance at almost any good commentary on this passage will show — that we should not take this instruction, or indeed, any of the teachings of the apostles, as somehow lacking in authority. 1 Corinthians 7:12 is not just Paul’s personal opinion; it is the authoritative instruction of an apostle of the Lord.