This is not just a response to put Satan off. But, more importantly, it is a statement of SpiritualLaw which clearly elevates the importance of every WordOfTheLord. We cannot experience AbundantLife without abiding in His Word.
Just as food is necessary for PhysicalLife, the WordOfGod is necessary for SpiritualLife. the Lord is a Spirit so we can only relate to Him in Spirit and in Truth by faith. We need the HolySpirit of the Lord and we need the WordOfTheLord.