This vegetarian dish is refrigerated overnight so the flavors can develop.
Cover wheat berries with cold water by 2 inches in a large saucepan. Cover; bring to a boil. Uncover; reduce heat, and simmer until tender, about 40 minutes. Drain; transfer to a serving bowl.
Whisk together lemon juice, mustard, honey, salt, and pepper. Pour in oil in a slow, steady stream, whisking until emulsified. Drizzle over wheat berries; toss.
Add fennel, cucumbers, celery, scallions, and parsley; toss. Cover; refrigerate 8 hours. Bring to room temperature.