In Exodus 20:14; Deuteronomy 5:18, the commandment against adultery signifies not only the violation of marriage vows, but also obscene acts, depraved language, and lustful thoughts.

In Matthew 5:28, a spiritual angel understands adultery to mean adulterating the goods of the Word and falsifying its truths. A celestial angel interprets it as denying the Divine of the Lord and profaning the Word. (Doctrine Regarding Sacred Scripture 67)

All the various kinds or degrees of adultery are spiritually understood by the prohibited conjunctions (Leviticus 18:24, 28.)

(Reference: Apocalypse Explained 235)