7881. 'And that day shall be to you for a memorial' means the essential nature of that state in worship. This is clear from the meaning of 'day' as state, dealt with in 23, 487, 488, 493, 2788, 3462, 3785, 4850, 5672, 5962, 6110; and from the meaning of 'memorial' as essential nature in worship, dealt with in 6888.
