In the Sermon on the Mount, Jesus frequently uses the phrase 'I say to you' to introduce teachings that often contrast with or expand upon traditional interpretations of the law. For example, He says, 'You have heard that it was said to those of old, 'You shall not murder,' and whoever murders will be in danger of the judgment. But I say to you that whoever is angry with his brother without a cause shall be in danger of the judgment.' Here, Jesus extends the commandment against murder to include anger, indicating that the spirit of the law goes beyond the letter. Another instance is when Jesus addresses adultery: 'You have heard that it was said to those of old, 'You shall not commit adultery.' But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart.' This teaching broadens the understanding of adultery to include lustful thoughts, emphasizing internal purity. Jesus also uses 'I say to you' to discuss divorce: 'Furthermore it has been said, 'Whoever divorces his wife, let him give her a certificate of divorce.' But I say to you that whoever divorces his wife for any reason except sexual immorality causes her to commit adultery; and whoever marries a woman who is divorced commits adultery.' Here, Jesus sets a stricter standard for divorce than was commonly accepted. In another teaching, Jesus addresses oaths: 'Again you have heard that it was said to those of old, 'You shall not swear falsely, but shall perform your oaths to the Lord.' But I say to you, do not swear at all: neither by heaven, for it is God's throne; nor by the earth, for it is His footstool; nor by Jerusalem, for it is the city of the great King.' Jesus advocates for a straightforward honesty that eliminates the need for oaths. Lastly, Jesus uses 'I say to you' to teach about retaliation and love for enemies: 'You have heard that it was said, 'An eye for an eye and a tooth for a tooth.' But I say to you, do not resist an evil person. But whoever slaps you on your right cheek, turn the other to him also... You have heard that it was said, 'You shall love your neighbor and hate your enemy.' But I say to you, love your enemies, bless those who curse you, do so good to those who hate you, and pray for those who spitefully use you and persecute you.' These teachings promote non-retaliation and unconditional love, challenging conventional attitudes towards justice and enmity.

In His Sermon on the Mount, Jesus restates God's original intent on the subject of divorce. He says, "I say to you, whoever divorces his wife for any reason except sexual immorality causes her to commit adultery, and whoever marries a woman who is divorced commits adultery." This statement directly challenges the common understanding among the Jews of the time, who believed that a man could divorce his wife simply by giving her a certificate of divorce. Jesus asserts His authority over this matter, indicating that His teaching supersedes the traditional interpretation of Moses' law, which allowed for divorce with a certificate.