Open the cans of kidney beans, chickpeas, and green beans. Rinse and drain them thoroughly.

Chop the bell pepper, red onion, and celery into small pieces.

In a small bowl, whisk together the olive oil, apple cider vinegar, Dijon mustard, salt, and black pepper until well combined.

In a large mixing bowl, combine the beans, chopped vegetables, and dressing. Toss gently to combine.

Chill in the refrigerator for at least 30 minutes before serving for the best flavor.