Imagine you're wearing nice clean clothes, and a kid comes along and throws a mudball at you. So annoying, right? You just want to grab some mud and throw it right back! But if you do that, your hands get dirty too, and the fight will never end.
The Bible says we shouldn't "get even" when someone does something annoying (like taking a toy without asking or saying something mean). Instead of hitting or yelling back, what do we do? We call in the Authority (dad, mom, or the teacher). When we let our Father in Heaven (and our parents) handle it, we keep a clean heart!