It is generally recommended to rinse lentils before cooking them to remove any debris or impurities [1]. However, forgetting to rinse them before adding them to your soup does not necessarily mean that the meal is unsafe to eat.

Here are a few points to consider:

1. Debris and stones: Rinsing lentils helps to remove any stones or foreign matter that may be present. While it is rare to find stones in lentils, it is still a good practice to sift through them before cooking [1].

2. Grit and chaff: Lentils are small in size and can sometimes have bits of grit or chaff clinging to them. Rinsing helps to remove these particles, ensuring a cleaner final dish [3].

3. Digestion: Some people prefer to soak lentils for an extended period and discard the water before cooking. This step can help remove substances that may cause indigestion [2]. However, if you have not soaked the lentils, rinsing them can still help improve their digestibility.

While not rinsing lentils may not pose an immediate safety risk, it is generally recommended to rinse them before cooking to ensure a cleaner and more enjoyable meal. If you have already cooked the soup, you can still enjoy it, but be mindful of any potential debris or grit that may be present.

Learn more:

1. Everything You Need to Know About Lentils
2. paranoia. again. forgot to wash lentils before throwing them in soup. | Mumsnet
3. What Are Lentils? Plus, How to Cook Them - Forks Over Knives