Read Matthew 5:27-30

“So if your eye—even your good eye—causes you to lust, gouge it out and throw it away. It is better for you to lose one part of your body than for your whole body to be thrown into hell.” Matthew 5:29 (NLT)

God prioritizes relationships, especially the intimate relationships between men and women. So He commands us to respect that relationship so fully that we would give up anything rather than let lust reign in our minds or bodies. Only in this way can we maintain both our own intimate relationships and our brotherly (sisterly) relationships with the greater community of believers.