Three common commercial abuses are concealing a known defect, giving less than the agreed quantity, and making an untruthful oath to persuade a buyer. These make the warning concrete.
Example: two sellers offer the same product. One discloses a defect and takes a fair price; the other conceals the defect to obtain more money. Both are trading, but their conduct is ethically different.
إِلَّا مَنِ اتَّقَى وَبَرَّ وَصَدَقَ makes the distinction clear. Trade itself is legitimate; oppression and dishonesty in trade are blameworthy.