Train them to have a habit of always redeeming the time.
Idleness is the devil's best friend. It is the surest way to give him an opportunity of doing us some harm. An idle mind is like an open door, and if Satan does not come through it himself, it is certain he will throw something in to arouse bad thoughts in us.
No created being was ever meant to be idle. Service and work is the appointed portion of every creature of God. The angels in heaven work—they are the Lord's ministering servants, always doing His will. Adam, in Paradise, had work—he was appointed to work and take care of the garden of Eden. And man, weak, sinful man, must have something to do, or else his soul will soon get into an unhealthy state. We must keep our hands busy, and our minds occupied with something, or else our imaginations will soon ferment and breed mischief.
And what is true of us, is true of our children too. The Jews thought idleness was an absolute sin: it was a law of theirs that every man should train his son in some useful trade—and they were right. They knew the heart of man better than some of us appear to today.
Idleness made the wicked city of Sodom what she was. [Ezekiel 16:49] Idleness had a lot to do with King David's awful sin with the wife of Uriah. I see in the Book of 2 Samuel, chapter 11, that Joab went off to war against the Ammonites, "but David remained in Jerusalem." Was that not idleness? And it was during that time of idleness that he saw Bathsheba—and the next step we read of is his tremendous and miserable fall into the sin of adultery.
Truly, I believe that idleness has led to more sin than almost any other habit that could be named. I suspect it is the mother of many sins of the flesh—the mother of adultery, sexual immorality, drunkenness, and many other deeds of darkness that I do not have time to name. Let your own conscience say whether I speak the truth or not. You were once idle, and immediately the devil knocked at the door and came in.
And why should this surprise us—everything in the world around us seems to teach the same lesson. It is the still water which becomes stagnant and impure: the running, moving streams are always clear. If you have machinery, you must run it now and then, or it soon begins to rust or break down. If you have a horse, you must exercise him; or he will not be strong for regular work. If you want to have good bodily health yourself, you must exercise. If you always sit still, then in time your body will complain. And so is it with the soul. The active moving mind is a hard target for the devil to shoot at. Try to be always full of useful employment, and thus your enemy will find it difficult to get room to plant evil thoughts.
My friend, I ask you to set these things before the minds of your children. Teach them the value of time, and try to make them learn the habit of using it well. It pains me to see children wasting time. I love to see them active and industrious, and giving their whole heart to all they do; giving their whole heart to lessons, when they have to learn—giving their whole heart even when they are playing.
But if you really love your children, then let idleness be counted as a sin in your family.