Note that His answer deals first with an example of similar breach of ceremonial law, and then rises to lay down a broad principle which governed that precedent, vindicates the act of the disciples, and draws for all ages a broad line of demarcation between the obligations of ceremonial and of moral law. Clearly, His adducing David's act in taking the shewbread implies that the disciples' reason for plucking the ears of corn was not to clear a path but to satisfy hunger. Probably, too, it suggests that He also was hungry, and partook of the simple food.
Note, too, the tinge of irony in that 'Did ye _never_ read?' In all your minute study of the letter of the Scripture, did you never take heed to that page? The principle on which the priest at Nob let the hungry fugitives devour the sacred bread, was the subordination of ceremonial law to men's necessities. It was well to lay the loaves on the table in the Presence, but it was better to take them and feed the fainting servant of God and his followers with them. Out of the very heart of the law which the Pharisees appealed to, in order to spin restricting prohibitions, Jesus drew an example of freedom which ran on all-fours with His disciples' case. The Pharisees had pored over the Old Testament all their lives, but it would have been long before they had found such a doctrine as this in it.
Jesus goes on to bring out the principle which shaped the instance he gave. He does not state it in its widest form, but confines it to the matter in hand--Sabbath obligations. Ceremonial law in all its parts is established as a means to an end--the highest good of men. Therefore, the end is more important than the means; and, in any case of apparent collision, the means must give way that the end may be secured. External observances are not of permanent, unalterable obligation. They stand on a different footing from primal moral duties, which remain equally imperative whether doing them leads to physical good or evil. David and his men were bound to keep these, whether they starved or not; but they were not bound to leave the shew bread lying in the shrine, and starve.
Man is made for the moral law. It is supreme, and he is under it, whether obedience leads to death or not. But all ceremonial regulations are merely established to help men to reach the true end of their being, and may be suspended or modified by his necessities. The Sabbath comes under the class of such ceremonial regulations, and may therefore be elastic when the pressure of necessity is brought to bear.
But note that our Lord, even while thus defining the limits of the obligation, asserts its universality. 'The Sabbath was made for man'--not for a nation or an age, but for all time and for the whole race. Those who would sweep away the observance of the weekly day of rest are fond of quoting this text; but they give little heed to its first clause, and do not note that their favourite passage upsets their main contention, and establishes the law of the Sabbath as a possession for the world for ever. It is not a burden, but a privilege, made and meant for man's highest good.
Christ's conclusion that He is 'Lord even of the Sabbath' is based upon the consideration of the true design of the day. If it is once understood that it is appointed, not as an inflexible duty, like the obligation of truth or purity, but as a means to man's good, physical and spiritual, then He who has in charge all man's higher interests, and who is the perfect realisation of the ideal of manhood, has full authority to modify and suspend the ceremonial observance if in His unerring judgment the suspension is desirable.