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.

In Matthew 5:33-37, Jesus addresses the matter of oaths with a profound declaration to His disciples, emphasizing the spirit of the law. He begins by summarizing the traditional teaching with, "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.'" With authority, He then transforms this understanding, stating, "But I say to you, do not swear at all." This bold command abolishes oaths among His followers, urging them to abandon such practices entirely. He specifies, do not swear 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; nor even by one's own head, as humans lack the authority to validate truth through themselves. His instruction is clear and absolute, reinforced by the Greek term "holos," meaning completely or wholly, leaving no room for exceptions among the elect. Jesus further teaches, "Let your 'Yes' be 'Yes,' and your 'No,' 'No,'" using a Hebraic repetition to strengthen the command to speak truth without qualification. He asserts that truthful people have no need to validate their words with oaths, as their integrity should stand alone. Any necessity for oaths stems from an atmosphere of distrust, which should be absent among His people. Thus, He calls His disciples to embody truth in all speech, rendering oaths unnecessary and irrelevant in their relationships with one another.

In Matthew 5:38-42, Jesus sets a high standard for His disciples, teaching them to avoid conflict and retaliation in personal matters. He begins by referencing the well-known principle, "An eye for an eye and a tooth for a tooth," and counters it with His own instruction, saying, "But I tell You, do not resist an evil person." He urges His followers to respond to personal insults and offenses with patience and humility, rather than seeking to get even. If someone slaps You on the right cheek, turn the other also, accepting the shame without responding in kind. If someone seeks to take Your tunic through a legal dispute, give them Your cloak as well, surrendering what is necessary to settle the conflict and establish peace. When compelled to go one mile, go with them two, showing love even to enemies by exceeding what is required. And to those who ask of You, give with a generous heart, not brushing them off, but being thoughtfully ready to help, even if it causes personal loss. Through these commands, He calls His disciples to a spiritual ideal, to act with the mind of Christ, sacrificing personal rights and interests to mitigate conflict and restore peace, reflecting His character in a world prone to escalation and feuds.

In the Sermon on the Mount, Jesus challenges the common beliefs of His time with radical teachings through His "But I say to you" passages. He refutes the notion of hating one's enemies, commanding His disciples to love their enemies, bless those who curse them, do good to those who hate them, and pray for those who spitefully use and persecute them. This command stands in stark opposition to human nature, which often reacts with aggression or retaliation when faced with hostility. Yet, He insists that His followers override these natural impulses and respond with divine love and kindness, reflecting the very character of God. Jesus explains that such actions are essential to becoming sons of the Father in heaven. He demonstrates that God Himself provides sun and rain to both the just and the unjust, actively showing love and provision even to His enemies. By following this example, His disciples reveal their identity as children of God, striving to match their behavior with the divine nature. He emphasizes that there is no merit in showing kindness only to those who love us, as even sinners do this. True growth and profit come from treating opponents with the same love and care as close family or friends, despite their hatred. In the culmination of these teachings, Jesus sets an extraordinary standard, declaring, "You shall be perfect as the Father in heaven is perfect." This perfection is not merely about adhering to the law but about embodying the righteous and holy character of the Most High God. He defines perfection as attaining the purpose for which we were designed—expressing limitless love, kindness, goodness, patience, peace, forbearance, and mercy toward all, including enemies. This is the goal He sets for His followers, an impossible standard for human effort alone, yet one He supports us in reaching as we strive to reflect His nature in our thoughts, words, and actions.

In Matthew 5, verses 17 through 20, Jesus Christ emphasizes critical teachings with the phrase "I say to you," underscoring their importance. In verse 18, He declares, "For assuredly, I say to you," affirming that the law remains steadfast and will not pass away until all is fulfilled. He insists that not even the smallest part of the law will be removed, emphasizing its enduring presence. In verse 20, He states, "For I say to you," revealing that acceptable righteousness must surpass mere obedience to rules, as exemplified by the Pharisees. He asserts that their righteousness is insufficient for entrance into the Kingdom of God, highlighting that a deeper, more genuine righteousness is required. Through these statements, Jesus Christ stresses the lasting significance of the law and the need for a righteousness that exceeds superficial adherence to regulations.

In the Sermon on the Mount, as recorded in Matthew 5, Jesus Christ delivers profound teachings through His "But I Say to You" statements, aiming to restore the divine intent of the law. He seeks to guide His disciples beyond the narrow, legalistic interpretations of the Pharisees, expanding the commandments to encompass broader principles of human behavior. Specifically addressing the seventh commandment against adultery, He emphasizes its wide-reaching implications, covering a spectrum of sexual perversions and faithlessness that God abhors. His desire is for His people to uphold loyalty, fidelity, and the sanctity of covenants, reflecting His deep disdain for any form of sexual immorality or betrayal. In Matthew 5:28, through His declaration, "But I Say to You," Jesus expands the understanding of adultery in three significant ways. First, He directly challenges the prevailing Jewish interpretation that largely held women accountable for adultery, making it clear that men are equally culpable. He states that whoever looks at a woman with lust has already committed adultery in his heart, targeting men as primary offenders while implying that all, regardless of gender, are subject to this principle. Second, He broadens the scope of the commandment beyond marital status or age, declaring that anyone—whether young or old, married or unmarried—who looks with lust upon another has committed a form of sexual immorality. By not limiting the sin to physical acts within or outside marriage, He includes all illicit sexual thoughts and desires under this prohibition, emphasizing that such behavior, if unrepented, bars one from the Kingdom of God. Third, He identifies the heart as the origin of adultery and fornication, revealing that sin begins with inner thoughts and desires, not just physical actions. Just as anger equates to murder in His earlier teaching, lust in the mind constitutes sexual immorality. He stresses that even without a physical act, a lustful thought corrupts the heart, rendering it impure and in need of cleansing to align with the purity required to see God. Further, in Matthew 5:29-30, Jesus uses hyperbolic language to underscore the severity of sexual sin, urging drastic measures to avoid it. Though not advocating literal self-mutilation, He conveys the necessity of sacrificing anything—however valuable—that leads to sin, prioritizing purity and entry into the Kingdom of God over worldly attachments. He illustrates the progression of lust from the heart to the eye and then to the hand, showing how internal desires can lead to visual temptation and ultimately to physical acts of immorality, including self-gratification, which He deems equally sinful. His teaching ultimately calls for a life of purity and sanctification, urging His followers to reject sexual immorality in all its forms. While He forbids such sins in the strongest terms, He also offers a path of repentance, encouraging those who have fallen to cease sinning and to live in alignment with His standards, ensuring their place in the Kingdom of God.