I have some sympathy to DN's arguments here. In the Matt 12 text, Jesus certainly seems to be saying that the letter of the OT law can indeed be broken without "sinning". As background, consider Exodus 31:14-15:
"Observe the Sabbath, because it is holy to you. Anyone who desecrates it must be put to death; whoever does any work on that day must be cut off from his people. For six days, work is to be done, but the seventh day is a Sabbath of rest, holy to the LORD. Whoever does any work on the Sabbath day must be put to death."
Maybe Jesus was not breaking the Law in respect to the matter of picking grains, but He presents the hypothetical about pulling a sheep out of a pit - that certainly seems like work. The whole flavour of the Matt 12 passage (the first 14 verses) suggests to me that Jesus would say it would be OK for doctors to do emergency surgery on the Sabbath (were that possible in those days) without being guilty of sin. Yet this would clearly be work by any reasonable interpretation.
It seems to me that any efforts to reconcile Matt 12 with a claim that Jesus never allowed breaking of the Exodus 31:14 mandate requires such a dramatic reworking (no pun intended) of the term "work" as to render it meaningless.
What are your thoughts, Wavy?