Two views of what it means that the Son of Man is Lord of the Sabbath:
The Sabbath was meant as a blessing to Israel (Deuteronomy 5:14; Mark 2:27), and not as an end in itself. What applied to Israel—that it was not to be a slave of the Sabbath but to use it as a means, as that a master does his property—applies infinitely more to Jesus, the true Israel.
In Matthew 12:8 Jesus calls himself the
Son of Man
to show that he is the One who, while humbly preaching as a man, is also the Lord of the Sabbath. This does not mean that Jesus set up the Sabbath, but that he has authority to say how it should be observed. He can command or permit Sabbath laws to be set aside, because they are not moral but ceremonial laws.
Interpretation 1:
The Sabbath was originally intended as a gift and as a blessing to Israel (Deuteronomy 5:14; Mark 2:27), and not as an end in itself. What applied to Israel—that it was not to be a slave of the Sabbath but to utilize it as a means, the same way that a master does his property—applies in an unlimited measure to the Son of Man, the true Israel (see Matthew 12:5–6).1
Interpretation 2:
In Matthew 12:8 Jesus refers to himself as the Son of Man
to amplify that he is the One who, although humbly preaching as a man, is also in reality the Lord of the Sabbath. This does not mean, in view of the context, that Jesus instituted the Sabbath, but that he has the authority to determine how it ought to be observed. He can command or permit that the Sabbath laws—which he himself in principle accepted—be set aside, precisely because they are not moral but ceremonial laws. Transgression or deviation can be necessary in order to serve God in truth. Even among men, in times of war for example, laws are sometimes suspended. The main point, however, is that Jesus here gives the ultimate reason why his disciples can pluck heads of grain on the Sabbath, namely that he as the Lord of the Sabbath has the authority to set aside the ceremonial law, and to allow others to do so.2
7 And if you had known what this means, ‘I desire mercy, and not sacrifice,’ you would not have condemned the guiltless.