Can I freeze hot soup?
It is better to let it cool down a little, because the hot items put into the refrigerator can raise the temperature inside. 

If your refrigerator gets warm, it can cause harmful bacteria to grow on your food. 

This can result in food poisoning, and the damage of the dairy products mainly (then you will have to get rid of them). It's better to be safe and wait for the food to cool first.

To cool them quickly, you can place them in a cold bath containing some ice cubes.