From John O’Brien’s The Life of Christ:
The Sermon on the Mount, with its glorious beatitudes, has stirred the hearts of men of every race and faith and has given them a vision of conduct so noble and sublime as to make them feel they are peering into the perfection of heaven. Even skeptics and the gross of heart find their barriers suddenly crumbling like the walls of Jericho before its trumpet peals, and tributes to its irresistible beauty and eternal truth come involuntarily from their grudging lips. The universal and unfailing response of the human heart to its divine beauty is the most authentic proof of the right of men to exist in the immeasurable universe. It is the warrant for the soul’s invincible spurning of the open grave as its final resting place, the patent of its worth, and the title deed to its eternal destiny. He who has read it, if only once, and has felt no stirring in his heart and heard no echo of its celestial music in his soul, deserves our pity and our love beyond all other men, because something precious beyond all price has died within him.
The throng which flocked around the Master on the plateau of that mountain was indeed a varied one: in it were the chosen Twelve, the larger group of disciples, and people who had some “from Galilee and Decapolis and Jerusalem and Judea, and from beyond the Jordan.” They had some to him because of His miracles and because He preached with authority and not as the Scribes and Pharisees.
Artists who depict the scene rarely portray in the countenances of the listeners any of the amazement and even the stupefaction which most of them must have experienced as they heard truths never before uttered and things of which they had never dreamed. When He spoke, they felt as if a door leading to the inner sanctuary of their souls had suddenly been opened and they were beginning to experience a new moral resonance. From the hidden depths of consciousness they were hearing a summons to a way of life strangely new.
Here was a code of conduct which was contrary to what they had ever heard from the lips of the Scribes and Pharisees and the doctors of the law. It was contrary to the conceptions which had been customary not only in pagan lands but also in Israel since the memory of man.
Like the people of other lands, the Israelites looked upon wealth as a blessing from God for leading a good life, and on poverty and sickness as a curse for sin. To them, a holy indifference to material things was just short of being incomprehensible. Into their false trust in wealth, Christ’s first words cut like a scythe swinging through weeds. One after another of their idols of clay came crashing in fragments down to earth. Spellbound, amazed, stupefied, they listened to these startling pronouncements, but deep down in their souls there was a sounding board never reached before, which slowly began to reverberate to these truths.
It’s worth noting that Bossuet begins his Meditations on the Gospel with an exposition on The Sermon on the Mount. He notes that this sermon “contains the chief precepts of the New Law…” Beginning with this, his Meditations focus on the two ends of Our Lord’s ministry: the start (the Sermon on the Mount) and the end (the “Last Week of the Savior,” what we normally refer to as Holy Week or Passion Week.)
The revolutionary content of the Sermon on the Mount is something that too many Christians downplay, to their–and our–peril.