No, there's no need to soak the lentils first. Simply rinse the lentils and add to the soup as per the recipe. As the red lentils are split, they cook quickly and break down to a puree which thickens the soup. Unlike brown lentils or green lentils, they don't hold their shape when cooked, making them excellent to use in soups, dahl, curries, dips, and so much more!