In Matthew 12:36, what does Christ mean when he says, "For every idle word ... [man] shall give an account"? What is an "idle word"? Does "give an account" mean "suffer punishment" or "be required to explain"?
"Brood of vipers! How can you, being evil, speak good things? For out of the abundance of the heart the mouth speaks. A good man out of the good treasure of his heart brings forth good things, and an evil man out of the evil treasure brings forth evil things. But I say to you that for every idle word men may speak, they will give account of it in the day of judgment. For by your words you will be justified, and by your words you will be condemned"(Matthew 12:34-37).
Have you ever heard someone say, "I didn't really mean that! I wasn't thinking." Perhaps you've said something similar yourself. An idle word is one that you said without careful consideration. Jesus' point is that you can tell a lot about a person's character, not by the major things they say, but by the little things which slip out when they aren't putting much effort into being careful.
When we go before God on Judgment Day, God will review everything we have done and said while on earth. It won't be limited to only the major events of our lives, but He will consider the small things we let slip when we weren't on guard because those things are more reflective of who we are than anything else. We will have to explain why we said what we said. The phrase "given an account" literally means "give words."
While Jesus is warning us that there will be no excuses before God, his point is useful in dealing with people. You can't read a man's mind or see into his soul as God can, but you can pay attention to what a person says. The little things which slip out when a person thinks no one is listening, or the things blurted out when a person wasn't thinking, are more accurate insights into the character of a person than all his considered pleas.