As the initial chapters of Matthew’s Gospel indicate, Matthew labored to present the kingship of Jesus Christ. In the Sermon on the Mount in Matthew 5-7, Jesus explained how His disciples should understand the Old Testament in light of His arrival and reign. Jesus argued that since He had come to fulfill the law, His followers should practice perfect, inside-out righteousness and enjoy the Father’s blessing.
Matthew’s comment, “When Jesus had finished this sermon, the crowds were astonished at His teaching, because He was teaching them like one who had authority, and not like their scribes” (Matt 7:28-29), placed Jesus in a different class than Israel’s other teachers. The crowd’s reaction showed the supremacy of Jesus; there had never been one like Him. Jesus had not come to destroy the Law or the Prophets, but to fulfill—to show His disciples the true intent of the Old Testament witness and establish the high moral standards that accord with a relationship with the Father.
(1) In Matt 5:21-26, Jesus commanded His disciples to avoid anger the way that Moses had commanded Israel not to murder. Jesus applied the sixth commandment, “Do not murder” (Exod 20:13; Deut 5:17), to the attitudes and thoughts of His followers. Jesus warned the disciples that if they even just cursed their brother, they would be in danger of hell (Matt 5:22).
(2) In Matt 5:27-30, Jesus warned His disciples to flee from immorality and thus avoid breaking the commandment forbidding adultery. Jesus demanded that His disciples apply the seventh commandment, “Do not commit adultery” (Exod 20:14; Deut 5:18), to their eyes and heart inclinations. Extremes were in order. The commitment to follow Christ required that disciples take whatever steps necessary to avoid sexual lust.
(3) In Matt 5:31-32, Jesus cited Deut 24:1 and forbade His disciples from seeking divorce except in cases of immorality. Moses required if an Israelite man wanted to divorce his wife, he had to give her a certificate of divorce to signify that he would never take her back. Jesus later said that Moses made the certificate law as a concession to Israel’s wickedness (Matt 19:7-8//Mark 10:4-5). Jesus demanded that His followers look to the pattern of a man leaving his parents and being united to his wife (Gen 2:24) and persevere in their marital commitment according to God’s will.
(4) In Matt 5:33, Jesus cited Moses’ laws against breaking oaths as a basis for avoiding oaths altogether. In various places, Moses commanded Israel to keep their word. In Leviticus 19, Moses argued that Israel’s behavior, including truthfulness (Lev 19:18), was to reflect God’s holiness. Moses’ broader teaching about oaths in Numbers 30 also demanded that Israel keep their word (Num 30:2). The assorted commands of Deuteronomy 23 included the warning that oaths were to be taken seriously (Deut 23:21-23). Jesus’ teaching in Matt 5:33 closely reflects Moses statement in Deut 23:22. Since words matter, best to avoid swearing oaths entirely.
(5) In Matt 5:38-42, Jesus demanded that His disciples extend mercy rather than take revenge according to the law of Moses. In Exod 21:22-25, Moses commanded that if a man hit another man’s wife, the husband is free to exact judgement upon the offender just as the offender injured his wife. In Lev 24:20, Moses said that if a man permanently injured another man, the offender was to be punished with the same injury he had inflicted on the offended. In Deut 19:21, Moses established the policy that false witnesses were to be punished without mercy. Jesus’ command that His disciples to turn the other cheek, go the extra mile, give to the one who wanted to take.
(6) In Matt 5:43-48, Jesus required His followers to love their enemies. In Lev 19:18, Moses commanded Israel to love their neighbors as themselves. Jesus’ followers demonstrated God’s benevolence and perfect righteousness as they showed love to those who opposed them.
(7) In Matt 7:23, Jesus cited Ps 6:8 to warn His disciples that they would be in danger if they did not adhere to the high standards of the kingdom of God. In Psalm 6, the psalmist cried out asking God to deliver him from death and the evildoers who surrounded him. The psalmist and Jesus wanted companions that were characterized by covenant loyalty, those who would share with them in the blessings God promised to the faithful. Therefore, if at the judgement someone addressed Jesus as Lord but had not fulfilled Jesus’ laws in the Sermon on the Mount, that one would hear Jesus say, “Depart from Me, you lawbreakers” (Matt 7:23).