"At the same time they also learn to be idle, as they go around from house to house; and not merely idle, but also gossips and busybodies, talking about things not proper to mention" (1 Timothy 5:13).
This verse comes during Paul's instruction regarding care for widows by the local church. He explained to Timothy why younger widows were not to be put on the list to receive continuing support. The danger is that they learn to be idle, which leads to other sins -- in this case, being gossips and busybodies.
King David is an example of one who fell into sin as a result of idleness. His sin involved Bathsheba. It began with lust, and proceeded to adultery, deception, getting Bathsheba's husband drunk, and ultimately arranging to have him killed in battle.
How did this happen to David? Notice the verse at the beginning of this account: "Then it happened in the spring, at the time when kings go out to battle, that David sent Joab and his servants with him and all Israel, and they destroyed the sons of Ammon and besieged Rabbah. But David stayed at Jerusalem" (2 Samuel 11:1).
In these times, military conflicts were led by kings. It was "the time when kings go out to battle." But did the king of Israel go out to battle? No! "David stayed at Jerusalem" while all the men of Israel went out to war. Since he was at home, and not where he should have been, what would he do to pass the time? Well, one of the things he did was sin with Bathsheba.
We need to be busy. We all have much to do. Paul instructs to make "the most of your time" (Ephesians 5:16). There is nothing wrong with taking a break to relax every once in a while. But there is so much we need to do, and much good that we can do beyond our fundamental responsibilities. Idleness prevents us from doing these things and opens the door for sin. Good is not accomplished and evil often takes its place. Let us guard ourselves from idleness so as not to give Satan any advantage.