Heat the olive oil in a large pot over medium heat. Add the onion, carrots, and celery and cook until the vegetables soften, about 5 minutes.
Stir in the garlic and cook for 1 minute until fragrant.
Add the lentils, diced tomatoes, vegetable broth, and rosemary sprigs. Bring the mixture to a boil, then reduce to a simmer.
Cover and cook for 25 minutes until the lentils are tender.
Remove the rosemary sprigs. Stir in the white beans and kale. Cook for another 5 minutes until the kale wilts and the beans heat through.
Season with salt and pepper to taste before serving.