Sabbath and Sabbath law is complex, confusing, impossible and important. Unfortunately, in Jesus' day those who interpreted Sabbath observance lost sight of the purpose of Sabbath and attached so many proscriptions to it that the average person could never hope to know or observe them all.
The poor knew they could glean corn and other produce after the owners or tenant farmers had picked the field clean, and could do this on the Sabbath because gleaning was not considered work by most rabbis. The Pharisees, however, said that rubbing the grains of corn off the cob was a form of harvesting and preparing a meal, and this was forbidden on the Sabbath.
In truth, there were many rabbis who would have suggested that the poor be encouraged to glean on the Sabbath since doing deeds of mercy was not only permitted but required. Because Jesus knew this, he reminded his listeners that David took the bread of offering and gave it to his companions as an act of mercy.
Sabbath observances and rest have a very distinct purpose. Because we so often forget who we are and how much God loves us, we need to stop every seven days and remember the mercy of God. If God's mercy does not encourage us to act like God, especially on behalf of the poor, then the purpose of the Sabbath is lost, and we would be better off not observing it at all.
Today, look at the people around you, not with the eyes of the law, but with eyes of mercy.
Do you take Sabbath rest seriously?