What's in your heart?

“You brood of vipers, how can you who are evil say anything good? For out of the overflow of the heart the mouth speaks.” Matthew 12:34
The Bible talks about the heart quite a lot, and while we understand that it’s not referring to the physical organ that pumps blood around our body, sometimes it’s difficult to put your finger on what exactly it is. The heart is different to the soul – the two can be divided (Heb. 4:12). God refers to giving us a new heart (Ezek. 36:26). Here’s the way I’ve come to view it. Each person is comprised of spirit, soul, and body. The body contains the soul – the personality. Similarly, the soul contains the spirit, or heart. For an unsaved person, their spirit is dead, but for a saved person, their spirit has been given life through Jesus Christ. The Greek word for soul is psyche, from which we get ‘psychology’. But psychology can only go so far: to the soul level. It cannot probe the deepest levels of a person’s heart and spirit.
But there is one way we can tell what is in someone’s heart – or our own, for that matter. What is coming out of their mouth? If their words are uplifting, focused on God and not themselves, true, pure, right, etc. (Phil. 4:18), then you can be pretty sure that their spirit is alive and connected to the living God. If on the other hand, their words are harsh, biting, selfish, sarcastic, belittling, or full of foul language and sexual innuendo, this could well be an indication that they are not saved. At the end of the day, only God knows for sure where each person stands with Him. But the words that come out of our mouths are an overflow of what is going on in our heart. By our fruit, we will be known (Matt. 7:16-20, see also Heb. 13:15).