For the true principles of preaching are enshrined in that glorious mountain sermon. From it we learn what a Christian oration ought to be. We see that it should contain instruction in Gospel truths, illustrations from natural objects, warnings, and moral exhortations, and that considerable variety of matter may be introduced, so long as the essential unity of the piece be not interfered with. In this consists the difference between Christ’s model sermon, and the exhortations of those who went before Him. Jonah preached to the Ninevites, “Yet forty days, and Nineveh, shall be overthrown,” and that was his only subject. John Baptist preached in the wilderness, and on one point only, “Prepare ye the way of the Lord.” They confined themselves to a single topic, and that purely subjective, whereas a Christian sermon is to be both objective and subjective. It should be like Jacob’s ladder, reaching from God’s throne to man’s earth, with its subject-matter constantly ascending and descending, leading men up to God, and showing God by His Incarnation descending to man. A Spanish bishop of the seventeenth century thus speaks of the Sermon on the Mount, the model for all sermons, and the pattern upon which many ancient preachers framed their discourses. He quotes St. John, “I saw in the right hand of Him that sat on the throne a book written within and without, sealed with seven seals;” and this book, he says, is the life of our blessed Lord, written with the characters of all virtues—within, in His most holy soul; without, in His sacred body. It is sealed with seven seals. St. John continues, “I saw a strong angel proclaiming with a loud voice, Who is worthy to open the book, and to loose the seals thereof? And no man in heaven, nor in earth, neither under the earth, was able to open the book, neither to look thereon.” Who, then, was worthy to open that book? None save Christ Himself. He opened it in the Sermon on the Mount, wherein He taught all men to follow and observe the virtues which He practised Himself. Hearken and consider as He opens each seal:— “Blessed are the poor in spirit:” and behold Him at the opening of this first seal, poor and of no reputation. “Blessed are they that mourn:” and this second seal displays Him offering up prayers for us, “with strong crying and tears.” “Blessed are the meek:” and we see Him meek and lowly of heart, before the judgment-seat answering not a word. “Blessed are they that hunger and thirst after righteousness:” this fourth seal exhibits Him whose meat it was to do the will of Him that sent Him, and who on the cross could still cry, “I thirst,” in the consuming thirst for the salvation of our souls. “Blessed are the merciful:” and “His mercy is over all His works.” “Blessed are the pure in heart:” and who was purer than the Virgin Son of the Virgin Mother?