Whosoever looketh - Matthew 5:28
"But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart." (Matthew 5:28)
In "Word Focus", Dr. Glenn McClure writes:

Jesus made a definite point to inform the Pharisees that this commandment not only dealt with the external act, but also the secrets of the heart and the movements of the eye. Matthew 5:28 brings to mind two quotes of Wünsche: “The eye and the heart are the two brokers of sin.” “Passions lodge only in him who sees.” Within this short verse we find this truth revealed, and why Scriptures deal seriously with moral purity.
The word looketh on in the Greek is blepō, which literally means “to see.” It is not just sight, but is an intended look, an effort made to gaze upon something; the constant fixation of the eyes upon something to examine it. Metaphorically it implies directing the mind upon it or joyfully beholding it. “According to the literal meaning of the Greek, the man who is condemned is the man who looks at a woman with the deliberate intention of lusting after her” (Barclay, NDSB).
The words of Randolph O. Yeager seem appropriate on this subject: “Jesus is not condemning everyone who looks at a woman; only those who look at a woman for the specific purpose of illicit sexual fantasy. The look must be directed toward the woman with a specific purpose in mind — that mental adultery with her can be enjoyed. Many men have looked at women in a legitimate way and later, as a result of that look, have found themselves aroused to evil thoughts. This is not the situation that Jesus was describing. The evil intent must precede the look; thus the look is for an evil purpose. The mental adultery has already been committed before the gaze is directed at its object. This is the force of hēdē (already). . . . Note that epithumeō (lust) [used here in v. 28] is the word used in the tenth commandment (Thou shalt not covet)” (Renaissance New Testament).

Discussion: Why might some argue that what they look at has no effect on them spiritually?
Source: Biblical Family Values, Adult Teacher's Insights, page, 40.