It is impossible to give an adequate short answer to the question of what did Jesus teach. In fact, John, after writing a rather lengthy gospel, cautions that Jesus did many other things that were not recorded. This would no doubt apply to His teaching as well (see John 20:30–31 and 21:25). Theologians and Bible students have worked for centuries to come up with good summaries of Jesus’ teaching, but what follows is at least a beginning summary:
Jesus taught publicly to the crowds and also privately to His group of disciples. He also publicly denounced the Jewish religious leadership (Matthew 23).
Jesus upheld but reinterpreted the Old Testament Law. What is called “the Sermon on the Mount” is the longest section of Jesus’ public teaching in one sitting (Matthew 5—7; cf. Luke 6:20–49). Here Jesus teaches that it is not keeping the letter of the law, but the spirit of it that is important. One cannot be righteous by merely keeping the law in an outward fashion.
Much of Jesus’ teaching seems to have been intended to get hearers to realize their inadequacy to keep the law. For instance, when someone asked Jesus about the greatest commandment, He responded, “‘Love the Lord your God with all your heart and with all your soul and with all your mind.’ This is the first and greatest commandment. And the second is like it: ‘Love your neighbor as yourself.’ All the Law and the Prophets hang on these two commandments” (Matthew 22:37–40). In a similar context in Luke 15, the questioner realizes how difficult this really is and so attempts to justify himself. It was clear to him (and should be to all of us) that we cannot keep these commandments perfectly, and so we need a Savior. Jesus reached out to the outcasts and sinners who were closer to the kingdom than the “righteous” because they recognized their dire inadequacies (see Matthew 21:31; Luke 18:9–14; Mark 2:15–17).
The kingdom of God (or kingdom of heaven) is near. Jesus proclaimed that the kingdom of God was about to arrive and that He, as Messiah, was the one to usher it in. However, this kingdom was not the earthly, military, political kingdom that was often expected by the Jews. The kingdom of God was centered in a relationship to Jesus as King. The bulk of Jesus’ teaching in Matthew centers on the nature of the kingdom of God. Integral to this teaching was that He would die and rise again (Mark 9:31). This death was to pay for sins (Mark 10:45; Matthew 20:28).
Jesus often taught in parables, which are extended illustrations to explain spiritual truth. Some of the most famous parables of Jesus are found in Luke, such as the Good Samaritan (Luke 10:25–37) and the Prodigal Son (Luke 15:11–32). Depending on how they are categorized, there are between 30 and 40 parables of Jesus in the New Testament.
Jesus also claimed to be the Son of the God, a statement that the people understood to be a claim to deity (John 10:33). However, the term He used most often to describe Himself was “Son of Man,” based on the heavenly personage described Daniel 7:13–14.
While Matthew, Mark, and Luke contain much of the same teaching of Jesus, John records many teachings that are not contained in the other gospels. Perhaps most significant are the “I am” sayings and their explanations:
• “I am the bread of life. He who comes to Me shall never hunger, and he who believes in Me shall never thirst” (John 6:35).
• “I am the light of the world. He who follows Me shall not walk in darkness, but have the light of life” (John 8:12).
• “I am the door. If anyone enters by Me, he will be saved, and will go in and out and find pasture” (John 10:9).
• “I am the good shepherd. The good shepherd gives His life for the sheep” (John 10:11).
• “I am the resurrection and the life. He who believes in Me, though he may die, he shall live” (John 11:25).
• “I am the way, the truth, and the life. No one comes to the Father except through Me” (John 14:6).
• “I am the true vine, and My Father is the vinedresser” (John 15:1).
John also contains the longest account of Jesus’ private instruction to His disciples in one sitting (John 13—16).
No matter how one categorizes Jesus’ teachings, it becomes obvious that Jesus considered a response to Him to be the deciding factor in one’s relationship with God and ultimate eternal destiny. It is also interesting to note that, while many emphasize Jesus’ teaching on love, most of what we know about hell is also from Jesus.
Today, some Christians claim to be “Red Letter Christians.” In many Bibles, the words of Christ are printed in red. “Red Letter Christians” focus on the teachings of Christ in the New Testament (the red letters) and minimize other New Testament teachings. On a similar note, people sometimes say, “Jesus never mentioned anything about homosexuality (or some other topic), so I don’t talk about it, either.” The “Red Letter” emphasis misunderstands the teaching and authority of Jesus. Jesus affirmed the Old Testament and all the moral imperatives contained in it. The apostles who wrote the New Testament (under inspiration of the Holy Spirit) were speaking for Christ. When Paul writes about homosexuality or any other topic, he writes with the authority of Christ. Jesus promised that the Holy Spirit would remind His apostles of His teaching after He had ascended into heaven (John 14:26). Jesus commissioned the apostles, “All authority in heaven and on earth has been given to Me. Therefore go and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit, and teaching them to obey all that I have commanded you. And surely I am with you always, even to the end of the age” (Matthew 28:18–20). The apostles simply relayed and applied the teaching of Jesus to the infant church, and we find the record of this in the rest of the New Testament.
There is no better way to find out what Jesus taught than to read the whole New Testament—not just the gospels.