Greek Lentil Soup (Soupa Fakez)

3 cups uncooked lentils
12 to 15 cups hot water
1 cup oil
4 to 5 cloves garlic
1 onion, minced
2 stalks celery
2 medium carrots, minced
1 sprig rosemary
1 1/2 pounds tomatoes, peeled and strained or
    1 (30 ounce) can tomatoes
Salt and pepper, to taste
Vinegar (optional)

Soak the lentils overnight in cold water. Rinse and place in a large pot with plenty of water. Bring to a boil. Drain off this water and replace it with the 12 to 15 cups hot water. Add the remaining ingredients except the tomatoes and salt and pepper. Simmer for 45 minutes, then add the tomatoes and cook for about 20 minutes longer (until the lentils are soft). Season.

Serve hot.