Soak the chickpeas overnight (about 10 hours) to soften them and reduce cooking time.
Rinse the lentils and barley thoroughly under cold water to remove any dust or impurities.
Chop the onion and garlic finely.
Cut the celery stalks into small or medium pieces to release their flavor without overpowering the soup.
Heat a large pot over medium heat and add olive oil. Sauté the onion until it turns golden and fragrant.
Add the garlic and cook briefly until aromatic but not burnt.
Add the soaked chickpeas, rinsed lentils, and barley to the pot. Stir well to combine with the sautéed onion and garlic.
Season with salt, black pepper, cumin, and turmeric. Mix thoroughly so the spices coat everything evenly.
Pour in enough boiling water to cover the legumes by about 2-3 cm. Cover the pot.
When the water comes to a boil, reduce the heat to low and simmer gently for about 1 hour and 15 m, stirring occasionally.
When the chickpeas, barley and lentils are tender, add the celery. Cover again and cook for another 15 minutes to soften the celery and blend the flavors.
Taste and adjust seasoning if needed. The soup should be thick, hearty, and full of flavor.