Note: The parallel account in Matthew (12:1-8) is fuller, but only Mark has the words "when he had need", 25, and all of verse 27.
"Grain fields" could be translated "corn fields." However, the word denotes small grain, not corn. They were walking on a path, they were not trampling the grain. See Deuteronomy 23:25. What they were doing was not prohibited.
They were accusing Jesus of allowing His disciples to do something that was forbidden. The action itself was not wrong, but the Pharisees claimed that it was unlawful on the Sabbath day.
Kretzmann: The Pharisees did not abate their jealous, hawk-like watch over Jesus and His disciples for one minute. And the Lord, on His part, in no way attempted to escape from them.
The fact that they followed Jesus and His disciples out into the country shows how closely they kept an eye on Him.
Kretzmann: Here the Pharisees complained to the Lord about the disciples, although their accusation implied a criticism of the Master for permitting the pulling of the stalks, which they identified with threshing.
Only Mark records the words "when he had need." The account is found in 1 Samuel 21:1-6. David and his men were not starving, but were hungry. Jesus' disciples likewise were not starving but were hungry. By the way, the text does not say that Jesus plucked and ate. The Pharisees rivet their attention on the disciples and are holding Him responsible.
Any good, reliable commentary will solve the so called problem of whether Abiathar (Mark) or Ahimelech (1 Samuel) was the High Priest at Nob.
Read Leviticus 24:5-9 concerning the show-bread. It was changed every week. The show-bread which was brought out of the Holy Place was to be eaten by the priest. That's what Jesus is referring to here.
Jesus was a master in logic and debating. The Pharisees ask an illogical question and He counters with a logical one. They use the expression "which was not allowed", in verse 24, erroneously and He counters with "which was not allowed", in verse 26, correctly. What the disciples did was not a violation of the Law. What David did was a violation of the letter of the Law but the higher principle of necessity prevailed. An overwhelming argument.
Kretzmann: God's intention never had been to make the children of Israel slaves of the observance of the ceremonial law, and to bind them with fetters that would render life unpleasant for them. The Sabbath is thus only a means to an end.
Ylvisaker: We must always bear in mind that every ceremonial law is subordinated to the law of love.
Lenski: God cares more for the right spiritual condition of the heart than for the outward observance of his own ceremonial regulations.
Meyer: The demonstrative force of this citation depends upon a conclusion from the greater to the lesser. David in a case of necessity dealt apparently unlawfully even with the show-bread of the temple, which is yet far less lawful to be touched than the ears of grain in general.
Hendriksen: The Sabbath was instituted to be a blessing for men: to keep him healthy, and make him helpful, hence happy, to render him holy, so that he might calmly meditate on the works of his Make, might 'delight himself in Jehovah' (Isaiah 58:13-14), and look forward with joyful anticipation to the Sabbath rest that remains for the people of God (Hebrews 4:9).
Mark alone has verse 27. David actually set aside a ceremonial law because of need. The disciples ate because they had need. They were hungry. But what they then did was not even a violation of a ceremonial injunction. It is a beautiful piece of logic. An argument from the greater to the lesser. The Pharisees had to admit that David did no wrong. How much less could the disciples be accused of wrong in view of Deuteronomy 23:25?
Furthermore, the Sabbath was created as a blessing for man. It was a day of rest for all. Deuteronomy 5:14. However, cases of need were not a violation of the Sabbath.
The Son of man is God incarnate. He created the Sabbath for man's sake and blessing. Therefore He is Lord. The Hebrew word would be "Yahveh," the God of promise.
"Even" or "also." If the former, the meaning is: "Not only this and that but also." If the latter, the meaning is: "I am Lord of even that which you have misunderstood so miserably." Compare Luke 6:5.
Hendriksen: In the first part of his reply, Jesus argues from an analogous case the admissibility of infringing the law to satisfy hunger. In the second part he shows the nature of the law itself, that it is the servant of man, and not man the servant of the law, involving the lordship of the Son of Man over the law.
Bengel: The end of the institution of the Sabbath is the salvation (welfare) of man as to his soul and body. The Son of Man is bound to ensure this salvation; and, in order to bring about this end, He has authority over all things, and expressly over the Sabbath, inasmuch as it was made for man; and with a view to obtaining this end, He regulates aright the whole use of the Sabbath.
Ylvisaker: He says 'the Son of man,' not only 'the Son of God.' But if Jesus, as the Son of man, is Lord over the Sabbath, then this must be true likewise of His disciples, see Galatians 4:9-10; Colossians 2:16-17; Romans 14:5-6.
Note: Read the following passages in succession:
The Sabbath was an Old Testament type of everlasting life through Jesus Christ. The Mosaic injunction of rest on the Sabbath was a sign between God and the Covenant people. The observance of the Sabbath was a matter of physical and spiritual blessing. It pointed to the God of promise, Jesus Christ, Who gives rest now and forever. Jesus is the author of the New Testament. He finally abrogated the Sabbath, the sacrifices, the Temple, all mere shadows of Himself. But He never violated the Sabbath Day. Look at Galatians 4:4-5. He put Himself under the Law. He observed the Passover and the Sabbath. He was circumcised. He redeemed all those under the Law. He put Himself under the Law. At the same time He was Lord even of the Law.
Perversion of the Word of God and rejection of the Son of man go hand in hand. The Pharisees accused the disciples of breaking the Law because they considered plucking heads of grain reaping. A perversion of the Word of god. Hand-in-hand goes their total aversion to the Savior, the Son of man. Compare Mark 7:8-13; Matthew 15:3,6; Matthew 23:23-24.
Luther's explanation of the third commandment is a gem.
The Pharisees' basic problem was work-righteousness. They based their acceptance with God on doing or not doing something. Furthermore, their "not doing" was not even Scriptural. The true believing Jews knew better, compare Galatians 2:15-16.