This verse is about honesty. When a buyer purchases an object and bargains on the honest price by purposely pointing out the negative aspects of the object, he buys it at a dishonest price, because the object bought is not worth the amount of money paid. Therefore, boasting about the object like boasting about your dishonesty.
Being Christians, we have to be honest in everything we do. With buying things, we have to give the money that is worth the object. If we bargain the price and pay less than the actual price, it is as though we are taking away God’s blessings from them. Technically, this is stealing. And in one of the Ten Commandments, it is written to “not steal” (Exodus 20: 15). Furthermore, boasting about something dishonest is evil in the eyes of our Lord (Psalm 52: 1-2). However, bear in mind that honestly does not only apply to financial aspects. As written in Psalm 101: 6, God love people who are “completely honest”.
So, fellow brothers and sisters in Christ, be honest in the presence of our Lord Jesus Christ! And if you do become dishonest, do not boast about it, for you are boasting your sins. Instead, repent in His Name Let your tongue speaks only of things that will glorify Him!