I tell you that anyone who divorces his wife, except for sexual immorality, makes her the victim of adultery, and anyone who marries a divorced woman commits adultery. –Jesus in Matthew 5:32

If the unbeliever leaves, let it be so. The brother or the sister is not bound in such circumstances; God has called us to live in peace. –Apostle Paul in 1 Corinthians 7:15

THE 1689 BAPTIST CONFESSION / WESTMINSTER CONFESSION
CHS. 24-25: “OF MARRIAGE AND DIVORCE”

1. Marriage is to be between one man and one woman: neither is it lawful for any man to have more than one wife, nor for any woman to have more than one husband, at the same time (Gen. 2:24; Mal. 2:15; Matt. 19:5–6).

2. Marriage was ordained for the mutual help of husband and wife, for the increase of mankind with legitimate issue, and of the church with an holy seed; and for preventing of uncleanness (Gen. 2:18; Gen. 1:28; 1 Cor. 7:2, 9).

3. It is lawful for all sorts of people to marry, who are able with judgment to give their consent; yet it is the duty of Christians to marry in the Lord; and therefore such as profess the true religion, should not marry with infidels, or idolaters; neither should such as are godly, be unequally yoked, by marrying with such as are wicked in their life, or maintain damnable heresy (Heb. 13:4; 1 Tim. 4:3; 1 Cor. 7:39; Neh. 13:25–27).

4. Marriage ought not to be within the degrees of consanguinity or affinity forbidden by the Word. Nor can such incestuous marriages ever be made lawful by any law of man or consent of parties, so as those persons may live together as man and wife (Lev. 18; Mark 6:18; 1 Cor. 5:1).

5. Adultery or fornication committed after a contract, being detected before marriage, giveth just occasion to the innocent party to dissolve that contract. In the case of adultery after marriage, it is lawful for the innocent party to sue out a divorce: and, after the divorce, to marry another, as if the offending party were dead.

6. Although the corruption of man be such as is apt to study arguments unduly to put asunder those whom God hath joined together in marriage: yet, nothing but adultery, or such willful desertion as can no way be remedied by the church, or civil magistrate, is cause sufficient of dissolving the bond of marriage: wherein, a public and orderly course of proceeding is to be observed; and the persons concerned in it not left to their own wills, and discretion, in their own case.

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William Heth, “Remarriage for Adultery or Desertion,” Remarriage After Divorce in Today’s Church.

Thomas Edgar, “Divorce & Remarriage for Adultery or Desertion,” Divorce and Remarriage: Four Christian Views.