Drain the soaked chickpeas in a sieve and bring to the boil in 1 1/2 liters of cold water. Skim off the foam and simmer covered for an hour.
Add the onions and carrots together with the olive oil and let simmer covered for about 30 minutes.
Test whether the vegetables are soft, then season with salt and pepper. Stir the parsley into the soup, bring to the boil briefly and serve with the lemon juice.