1. Matthew 5:28
"But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart."
Jesus revolutionizes moral understanding by elevating the standard from external behavior to internal heart condition, showing that adultery begins in the mind before expressing itself in action. The phrase "looks at a woman with lustful intent" uses "pros to epithymeēsai" (πρὸς τθὸ ἐπιθυμεῖν) - "for the purpose of lusting" - indicating deliberate, sustained desire rather than momentary attraction. The Greek "epithymeō" (ἐπιθυμέω) means to desire earnestly or long after, but in this context refers to sexual desire directed toward someone who belongs to another. Jesus declares this "has already committed adultery with her in his heart" (emoîcheusen autēn en tē kardia autou), using the aorist tense to indicate completed action - the sin is fully realized in God's sight. John MacArthur emphasizes that Jesus isn't condemning natural attraction or momentary temptation but the cultivated, sustained mental adultery that treats women as objects for selfish gratification. The "heart" (kardia) represents the center of moral decision-making where sin originates. Charles Spurgeon noted that this standard is impossible to achieve in human strength, driving us to depend on Christ's righteousness and the Spirit's power for purity. R.C. Sproul observed that this verse establishes the heart as the primary battlefield for holiness - external conformity without heart purity is merely hypocrisy. The practical application involves taking responsibility for our thought life and implementing strategies to guard our hearts and minds. (Desiring God)