I have a question about collisions?

Claussius statement of the second law of thermodynamic state that if there are two system in contact, the sole result is that the hotter body will give its heat to the cooler body. However according to thermodynamic probability, it's possible that the slow atom caused the faster atom to increase its speed, but the probability is close to zero, almost impossible to happen. Thus, if no work added, almost 100% hotter body will get cooler.