The stubborn and self-willed Galatians who wanted to cling to the old Jewish Law refused to accept in toto that Christ was the salvation for both Jews and Gentiles. They insisted that the Gentile converts keep the Mosaic Law including all its rituals. Paul had to come down quickly and severely on this fundamental error.
He argued as a rabbi with rabbis, quoting frequently from the Old Testament. He proved, from the Allegory of The Covenants and from Isaiah and Genesis, that the Law itself proclaimed its own temporary nature and that it would give way to the New Dispensation of the Spirit. The point was that the Mosaic Law and the New Dispensation were incompatible and could not co-exist, if one's faith was based on God's promises. Clinging to the Mosaic Law would have meant detracting from the Cross of Christ which was a unique and all-sufficing sacrifice. Such a fundamental error could not be tolerated.
Similiarly, Luke shows the stubbornness of the crowds around Jesus. They are rebuked for belonging to "a wicked age". Strong words indeed. Their stubborn persistence in asking for signs produces from Jesus the reminder that even the wicked people of Nineveh and the powerful Queen of the South had reformed when warned by Jonah and Solomon respectively.
Such stubbornness was an obstacle to recognising Jesus as the one true sign, the object of our faith.
Lord, strengthen our faith to withstand our own stubbornness and our insistence on listening to ourselves and not to You.