Some people believe it's acceptable for a couple to live together even before marriage, but world-renowned evangelist Billy Graham would beg to disagree.

One man wrote to Graham at The Kansas City Star, expressing his concern over his nephew who plans to move in with his girlfriend. When the letter writer told his nephew that he would be committing a sin, the young man just laughed at his uncle and said no one in today's society believes in celibacy anymore.

The writer's nephew even said he is not interested in God because the only thing he cares about is being happy.

In response, Graham said the young man's comments are saddening. "He's interested only in what's happening in the present moment, and he doesn't want anyone to interfere with what he's doing, including God," the evangelist wrote.

Even though the young man refuses to listen to his relatives, Graham said they should not stop warning him about the consequences of his actions. He said this young man needs God's love and guidance to enable him to confidently face the future, adding that he seriously needs to reassess how he views relationships.

Graham said people like this young man run a great risk of unhappiness in their relationships, which he said are doomed to fail because they sorely lack one thing: stability. "The reason is because, unlike marriage, they lack true commitment and can unravel at any moment. What happens if one of them gets bored or upset or finds someone more attractive?" he asked.

Earlier, the evangelist said that any sexual activity outside of marriage is a sin. Some might argue that God is withholding happiness in upholding celibacy, but He placed "fences" or boundaries around sexuality for a very important reason, Graham said.

"[God] knows that without them, we'll end up harming not only ourselves but also those around us, sometimes in very serious ways," he wrote. "Never forget: God gave us the gift of our sexuality, and He meant for it to be a joyous expression of love between a husband and wife. When practiced outside of marriage, however, sex becomes selfish and even manipulative — the opposite of true, self-giving love."