Drink water from your own cistern,
And fresh water from your own well.
Proverbs 5:15 (NASB)
Proverbs chapter 5 continues Solomon's entreaty to value wisdom. However, he focuses exclusively on the wisdom of avoiding adultery and the adulteress woman.
As an American, we are blessed beyond measure that we have almost universal access to clean, safe water. Most stores have a water fountain. Most businesses have a water fountain. I can turn on a faucet in my house and get all the clean water I need to bathe, wash or drink.
However, we've gotten so spoiled lately, that just plain tap water isn't good enough. We've gotten bored with the good, clean water and we've convinced ourselves that we need fancy bottled water.
Marriages can be the same. We see images of beautiful, sexy women on TV, movies and print. Air-brushed and edited to perfection, the idea is constantly displayed that "there's something BETTER out there for you". And we've convinced ourselves that "it's okay to look at the menu, just as long as you don't order".
Jesus, however, tells us that this is NOT true. "but I say to you that everyone who looks at a woman with lust for her has already committed adultery with her in his heart." Matthew 5:28 Just to look at a woman and desire her means that you are dissatisfied with the bride that you have already. It means that you are telling God "I know that you made this woman just for me, and that I've vowed to You to keep myself only to her, but she's not good enough anymore".