Jesus began His ministry after His baptism and subsequent temptation in the wilderness. Upon hearing that John was arrested, Jesus withdrew into Galilee, fulfilling Isaiah’s prophecy, “The people dwelling in darkness have seen a great light, and for those dwelling in the region and shadow of death, on them a light has dawned” (9:1, 2). Matthew states, “From that time Jesus began to preach, saying, ‘Repent, for the kingdom of heaven is at hand’” (4:17).
Following Matthew’s chronology, after calling the first apostles (Matthew 4:18–22), He went throughout Galilee, teaching in the synagogues and proclaiming the kingdom of God. Great crowds were following Him. Chapter five begins with a curious phrase, “Seeing the crowds . . .” This cannot mean that only then did He became aware of them. The kingdom of God was at hand and the King was among them. His teaching and healing were proof. The crowds followed Him, and His “seeing them” is in this kingdom context. Jesus stepped into Moses’ role, giving them His law. The Sermon on the Mount is the new covenant Sinai but without its terrifying sights and sounds. Nevertheless, the allusion to Mount Sinai is evident in many points.
Upon seeing the multitude, Jesus went up to the mountain and sat down in the tradition of rabbinic teachers. When He did so, His disciples came to Him. The tendency is to conclude that these disciples were the twelve men, whom He called apostles, that eventually made up the core of His earthly followers (Matthew 10:2). This is a mistake because in the previous chapter Jesus called the first of the twelve—Peter, Andrew, James, and John. We know of no others at that time, save possibly Philip (John 1:38, 39). So, who were these disciples? Great teachers had followers who were called disciples. Matthew said, “Great crowds followed him” (4:25). They witnessed the Messianic signs and believed that Jesus was the Christ. There is no accounting of their number, but it was likely in the hundreds. In Luke 10 Jesus appointed 72 out of that crowd whom He sent out on a special mission. (Interestingly, Jesus spent much of His ministry, not seeking to increase His following but discouraging them by showing the cost of discipleship [Luke 9:23–27].)
In setting down the conditions for discipleship, Jesus stepped into Moses’ shoes. The Sermon on the Mount sets forth the law of Christ that is to govern new covenant Christ-followers. In order to win some to Christ among the Jews, Paul wrote that he kept the Mosaic law. However, when among those not under the Mosaic covenant (Gentiles), he kept the law of Christ: “To those outside the law I became as one outside the law (not being outside the law of God but under the law of Christ) that I might win those outside the law” (1 Corinthians 9:21). Followers of Jesus are not under Sinai’s rule; thus, we are admonished, “Bear one another’s burdens, and so fulfill the law of Christ” (Galatians 6:2).