The Sermon on the Mount is very much a Jewish style collection and there are some parallels between Jesus’ teaching and discussions of the Law found in the Mishnah. For example, exchanging coins for tithes (Mt. 21:12, Maaser Sheni 2:7, Sheqalim), rules for healing on the Sabbath (in Shabbat, cf. Luke 6:6-11), fasting (in Taanit, cf Mt. 6:16-18), Marriage and divorce, (Ketubot, cf Mt. 5:31-32, 1 Cor. 7), Vows (Nedarim, cf Mt. 5:33-37), etc. Several of the “you have hear it said” topics in the Sermon seem very much based on the same sorts of rabbinic interests in the Mishnah.
This tells us something important about Jesus’ style of teaching: it was not unlike contemporary Jewish teachers. But more than this, it tells us something about Matthew’s collection of Jesus’ sayings into the Sermon on the Mount. Perhaps we can think of the discourses in the book of Matthew as a sort of proto-Mishnah, with a focus on only one teacher, Jesus.
In Matthew 5:21-48, Jesus discusses elements of the Law. Did Jesus come to abolish the Law? Rather than abolishing the Law, Jesus seems to be re-interpreting it in a somewhat radical manner. The first three of these examples seem to re-interpret and intensify the law, while the second three seem to interpret the Law which may make the command “lighter.” Jesus “goes beyond the Law” by returning to the heart of the Law.
In the first two cases, murder and adultery, Jesus takes the command of scripture and emphasizes the emotion underlying the sin. For murder, the real problem is anger and hatred. For adultery, the real problem is lust. Jesus says that one cannot claim to keep the commandments if they have been angry with their brother or lusted in their hearts. Other Jewish literature recognizes this as well. Sirach 9:1-9, for example, encourages the one who Fears the Lord to be careful what they look at in order to avoid adultery. Similar to Jesus, the wise person in Sirach 9 avoids the mental process which leads to lust in order to avoid lust.
Here is an example of this quasi-rabbinical application of the Law, through Jesus, to a contemporary issue. (Another though experiment, since people like those so much!) I think most Christians are going agree with Jesus that lusting in one’s heart is sinful, and this is usually used to point out that pornography is wrong. But what about the command to be careful about “murdering in your heart”? If a Christian says using a computer for pornography is wrong, why do we not also say using a computer for violence is wrong? Playing a violent video game is in fact “murdering in your heart” and ought to be seen as just as great a danger as viewing porn on a computer. Again, Christians agree watching a pornographic movie is sin, but then watch extremely violent movies. That Jesus chose to pair violence and sex in his teaching should be a powerful warning to modern Christians who filter one, but not the other.
Is this a fair application of the principles of the Sermon on the Mount? Why do Christians (rightly) condemn sexual content in entertainment, but not violence?