Prepare the dressing: In a bowl, combine the olive oil, vinegar, oregano, water, salt, and black pepper to taste. Whisk until combined.
Prepare the bread: If you have stale bread (at least 2-3 days old), simply cut it into cubes. If you only have fresh bread, toast it in the oven or in a toaster for a couple of minutes, until it becomes golden in color.
Prepare the salad: Thinly slice the onion, cut the tomatoes in half (or quarters if they are big) and place in a bowl with the chickpeas. Add the black olives (I used kalamata olives) and the bread cubes. Pour the dressing all over the salad and mix well.
Sprinkle the basil leaves all over and let it rest for a minimum of 20 minutes (but ideally a couple of hours) before serving.