In Luke 6, how is it not a sin that Jesus picks grain on the Sabbath?

The episode in question is recorded in Luke 6:1-5, with parallel accounts recorded in Matthew 12:1-8 and Mark 2:23-28.  Jesus and his disciples are walking through a grain field, and his hungry disciples begin picking the heads of grain, rubbing them in their hands to remove the husk, and eating the raw grain.  Pharisees accuse his disciples of breaking the Sabbath laws about labor.  Apparently to the Pharisees, picking a few heads of grain was the same as harvesting the entire field.  Jesus defended his disciples with several arguments.

First, he pointed out that David had eaten of the sacred bread in the tabernacle when he was hungry, and no one found fault with him for doing so  (Lk. 6:3-4).  He also cited how the priests worked on the Sabbath and were not condemned for doing so (Matt. 12:5).

Even more significantly, he points out that “the Sabbath was made for man, and not man for the Sabbath” (Mk. 2:27).  In other words, God intended the Sabbath to be a blessing rather than a burden.  To tell his disciples that they couldn’t even do something as minor as pick a head of grain off of a stalk to eat it when they are hungry was not the rest from work God had in mind for the Sabbath.  As Jesus also pointed out by citing Hosea 6:6’s “I desire compassion, and not a sacrifice” (Matt. 12:7), God placed more importance on relieving suffering and helping those in need than fulfilling man-made rituals.

Most importantly, Jesus is the Son of God, the Messiah, Deity himself.  He out-ranked their human traditions, their temple (Matt. 12:6), and the Sabbath itself (Lk. 6:5).  If anyone had the authority to determine what could or could not be done within the frame work of the Old Testament laws concerning the Sabbath, it was Jesus.  Since he was defending his disciples’ actions and thus condoning them, it is clear that no sin was actually taking place.