Matthew 12:2

But the Pharisees, when they saw it, said unto him, Behold, thy disciples do that which it is not lawful to do upon the sabbath.

This charge was false. God's law did not prohibit the preparation and eating of food on the sabbath day. At the conclusion of the interview, Jesus referred to his disciples as "guiltless" (Matthew 12:5). It is true, however, that the disciples had violated a Pharisaical "interpretation" of the law; and such interpretations were held even more sacred by the Pharisees than the law itself. In the Pharisees' view, the disciples were guilty of threshing wheat! Such pedantry, nit-picking, and magnification of trifles would also have made them guilty of irrigating land, if they had chanced to knock off a few drops of dew while passing through the fields! The Pharisees were out to "get" Jesus; and any charge was better than none.