New Defender's Study Bible Notes
19:7 writing of divorcement. Deuteronomy 24:1-4. Christ here confirms the Mosaic authorship of Deuteronomy.
19:9 except it be for fornication. The relatively easy divorce allowed in the Mosaic law was not intended in God’s original economy (Matthew 19:8). The only allowable grounds for divorce according to Christ is adultery. The Greek word for “fornication” (porneia) could include any sexual sin committed after the betrothal contract. On the other hand, Jesus did not even allow this exception in Luke 16:18. The conclusion would be that, even though adultery or fornication are permissible grounds for divorce and remarriage, it is still better to salvage the marriage if possible. See also Romans 7:2-3; I Corinthians 7:10-15.