en_tn/mat/05/28.md

But I say

Jesus agrees with God and his word, but he does not agree with the way the religious leaders have applied God's word. The "I" is emphatic. This indicates that what Jesus says is equally important to the original commands from God. Try to translate this phrase in a way that shows that emphasis. See how you translated this in Matthew 5:22.

everyone who looks on a woman to lust after her has already committed adultery with her in his heart

This metaphor indicates that a man who lusts after a woman is as guilty of adultery as a man who actually commits the act of adultery. (See: rc://en/ta/man/translate/figs-metaphor)

to lust after her

"and lusts after her" or "and desires to sleep with her"

in his heart

Here "heart" is a metonym for a person's thoughts. AT: "in his mind" or "in his thoughts" (See: rc://en/ta/man/translate/figs-metonymy)