On this occasion, Jesus did not wait for somebody to ask a question, as He did in Luke 4. He just went out and did what needed to be done. This episode shows God's purpose for the Sabbath very clearly. Jesus says, "You are loosed." When one is loosed, one is made free. The lesson is clear. This woman was in bondage to an infirmity, something Satan had afflicted her with.
On the other hand, there were the Pharisees. To them, the Sabbath was rules to obey—their rules, their traditions. To the ruler of the synagogue, then, the Sabbath was unfit for loosing somebody from his pain or from his infirmity.
Jesus calls him a hypocrite in verse 15. "Does not each one of you on the Sabbath loose [untie, free] his ox or donkey from the stall? So ought not this woman, being a daughter of Abraham, whom Satan has bound—think of it—for eighteen years, be loosed [freed, delivered, redeemed] from this bond on the Sabbath?"
How plain! Once we begin to see what Jesus did and talked about on the Sabbath, it becomes clear that He was magnifying its use. The Sabbath is the day of liberation; it is the day God blessed so that we can remain free and no longer be brought into bondage. (Incidentally, the verbs translated "loose" are the Greek word that means "to free.")
Does Jesus say, "Oh, it doesn't matter. We're going to do away with the Sabbath anyway"? No! Instead, He argues for a right, merciful evaluation of a person under a heavy burden and then using the Sabbath to relieve him of it. He is arguing for true values in the use of God's Sabbath.