Heat the olive oil in a frying pan over a medium heat. Fry the bread for about 5 minutes until golden brown all over, then add the garlic and cumin and cook for 1 more minute until the garlic is nutty brown.
Transfer to a mortar and pestle or food processor along with the vinegar, and mash to a paste.
Return the bread mixture to the pan and add the drained chickpeas.
Stir until the chickpeas have absorbed the flavours and are hot, then season with salt and pepper. If the consistency is a little thick, add some water.
Add the spinach and cook until just wilted, check the seasoning and serve.