ISB ~ 1 Corinthians 7 v10

not I but the Lord:Paul’s teaching on divorce is directly mandated by Christ (Mk 10:2-12; Lk 16:18). Couples are strongly discouraged from seeking divorce because of personal dissatisfaction with marital relations and companionship. Should they choose to separate, their options are twofold: “remain single” or “be reconciled” (1 Cor 7:11). Like Jesus, Paul leaves no legitimate room for remarriage, since the bond of sacramental marriage is lifelong and can be dissolved only by the death of one of the spouses (7:39; Rom 7:2-3; CCC 2364, 2382).

See essay:Jesus on Marriage and Divorce at Mt 19.