The Sermon on the Mount is the foundational ethical teaching of Christianity. It occupies three chapters in Matthew (5-7) and contains some of the most quoted words in human history. The Sermon opens with the Beatitudes (5:3-12) — a portrait of kingdom character. It continues with the "salt and light" metaphors (5:13-16) — the mission of kingdom people in a rotting world. Jesus then teaches about the Law: He did not come to abolish but to fulfill (5:17-20). He gives six "you have heard... but I say to you" antitheses (5:21-48) that radically deepen the Law: murder begins with anger, adultery with lust, oath-keeping with truth-telling, revenge with enemy-love. He moves to religious practice (6:1-18) — giving, praying, and fasting must be done in secret, for God's eyes only; and in the middle He gives the Lord's Prayer (6:9-13). He teaches about money, anxiety, and priorities (6:19-34): do not store up earthly treasures, do not worry, "but seek first the kingdom of God and His righteousness, and all these things shall be added to you" (6:33). He warns about judging others (7:1-6), commands persistent prayer (7:7-12), contrasts the narrow gate with the broad way (7:13-14), warns about false prophets (7:15-20), distinguishes genuine from false disciples (7:21-23), and closes with the parable of the wise and foolish builders (7:24-27). The crowds were astonished because He taught "as one having authority, and not as the scribes" (7:29). The Sermon is not optional advice for spiritual advanced students; it is the charter of the kingdom. Every Christian is obligated to know it, struggle with it, and obey it. Anyone who claims to follow Jesus but does not reckon with the Sermon on the Mount is not reckoning with Jesus.