a. properly: Romans 7:3; ὀφθαλμοί μεστοί μοιχαλίδος, eyes always on the watch for an adulteress, or from which adulterous desire beams forth, 2 Peter 2:14.

b. As the intimate alliance of God with the people of Israel was likened to a marriage, those who relapse into idolatry are said to commit adultery or play the harlot (Ezekiel 16:15ff; 23:43ff, etc.); hence, μοιχαλίς is figuratively equivalent to faithless to God, unclean, apostate: James 4:4 (where cf. Alford); as an adjective (cf. Matthiae, § 429, 4), γενεά ... μοιχαλίς: Matthew 12:39; Matthew 16:4; Mark 8:38. (Cf. Clement of Alexandria, strom. vi. c. 16 § 146, p. 292, 5 edition Sylb.)

Corresponding Greek / Hebrew Entries: • H5003 נָאַף (na'aph): This Hebrew term means "to commit adultery" and is often used in the Old Testament to describe both physical and spiritual adultery.
• H2181 זָנָה (zanah): This word means "to commit fornication, be a harlot, play the harlot," and is frequently used metaphorically to describe Israel's unfaithfulness to God.

Usage: The word μοιχαλὶς is used in the New Testament to describe a generation that is unfaithful to God, often in the context of spiritual adultery, where the people have turned away from God to pursue other idols or worldly desires.

Context: The term μοιχαλὶς appears in the New Testament as a descriptor of spiritual unfaithfulness. In the Gospels, Jesus uses this term to rebuke the people of His time, highlighting their lack of faith and their pursuit of signs rather than genuine belief. For instance, in Matthew 12:39 (BSB), Jesus responds to the scribes and Pharisees who demand a sign, saying, "A wicked and adulterous generation demands a sign, but none will be given it except the sign of the prophet Jonah." Here, μοιχαλὶς is used metaphorically to emphasize the spiritual infidelity of the people, who, despite witnessing Jesus' miracles and teachings, still seek further proof of His divine authority.

The use of μοιχαλὶς underscores a broader biblical theme of covenantal faithfulness. In the Old Testament, Israel is often depicted as an unfaithful spouse to God, pursuing other gods and breaking the covenant. This imagery is carried into the New Testament, where the term is applied to those who fail to recognize and accept Jesus as the Messiah, thus continuing the pattern of spiritual adultery.

The concept of spiritual adultery is a call to repentance and a return to faithfulness. It serves as a warning against the dangers of idolatry and the importance of maintaining a steadfast relationship with God. The use of μοιχαλὶς in the New Testament is a powerful reminder of the call to spiritual fidelity and the consequences of turning away from God.