17 But as God has distributed to each one, as the Lord has called each one, so let him walk. And so I ordain in all the churches. 18 Was anyone called while circumcised? Let him not become uncircumcised. Was anyone called while uncircumcised? Let him not be circumcised. 19 Circumcision is nothing and uncircumcision is nothing, but keeping the commandments of God is what matters. 20 Let each one remain in the same calling in which he was called. (1 Corinthians 7:17–20, NKJV)
What Paul taught about marriage in verses 10-14 applies a foundational and universal principle he now explains in verses 17-22 (24). (That the believer is not being under bondage to the unbeliever in verse 15 applies another foundational principle, verse 23.) Non-sinful relations and conditions of life do not affect one’s salvation in Christ. Therefore, it is right and good to “remain in the same calling” in which you were called (v. 18-20). Circumcision illustrates this, which is inconsequential concerning salvation. What matters is keeping God’s commands, and circumcision is not commanded for salvation. Similarly, marriage is not commanded for salvation, but it is allowed. We conclude with certainty that Paul is not giving permission to remain in a sinful relationship when one becomes a Christian, including sinful marriages (Rom. 6:1-2; Matt. 19:9). Every sinful action and sinful relationship must be repented of and abandoned when one becomes a Christian (Acts 2:37-38; 1 Cor. 6:9-11; 1 Thess. 4:1-5).