[For objects, the speaker may show two jars of preserves or jelly, one moldy and the other not.]
Suppose a man wanted to seal up some valuable liquid so that it would remain just as pure as it was when he first prepared it; how would he go to work?
In the first place, he would boil the liquid in the flask in which it was to remain, and when the boiling liquid was fairly running over and had driven out before it, as it expanded, every particle of the air, then he would quickly seal it up, and fasten the stopper in so thoroughly that not a particle of air could get in.
The reason for that is this: The air is filled with little substances, far too fine for any eye to see them, and yet these substances, as soon as they have a place to grow in, increase with wonderful rapidity, and at once make foul, and often discolor and thicken, all the liquids that are exposed to the air. Some day you will find that that is why jelly molds, and yeast ferments, and preserves work. But if the air is entirely driven away and kept away from the liquid we want to preserve, then we can keep it for a very long time.
I think you can learn a lesson from this about the way to keep yourselves pure in your words, and in your thoughts, and in your deeds. It is by filling your lives so full of good thoughts and good words and good deeds that the bad spirits that are all the time trying to creep into human lives have no room to get in, just as the air could not get into the flask when the water was boiling and running over.
The next time you feel yourselves tempted by any evil thought, go right away to some helpful book, or busy yourself with some kind and useful task, and see if you do not find that you have crowded out the bad thought, and kept it from doing any mischief in your lives.