In the temptation story, Jesus is quoting a scripture passage, introduced by the words "It is written." The focus at that point is Jesus acknowledging the truth and authority of God's word. He is saying in effect, God has spoken and I must submit to that word.
In the Sermon on the Mount, the focus is different. Jesus here is a rabbi teaching his disciples (Matthew 5.2), and the contrast in chapter 5 is between his teaching and the teaching of other Jewish authorities, such as the Pharisees or other rabbis. So when Jesus says "You have heard that it was said", this is not a reference to the OT scripture at all. It's a reference to interpretations of the scriptures.
For example, what does it mean that "You shall not murder"? Jesus' answer in Matthew 5.21-22 is that other teachers have limited the scope of the commandment to the physical act of killing someone. But Jesus' teaching is that the command is broken if and when I get angry with someone. This is presumably because the inward attitude is what leads to the outward action. The focus on the inner heart and spirit is a regular theme of Jesus' teaching.
This distinction between OT command and Jewish interpretations of that command is especially clear in Matthew 5.43-44. Here Jesus quotes teachers who say "Love your neighbour and hate your enemy." In fact this is not a command found in the OT. The only command that is found is to "love your neighbour", so "hate your enemy" is an addition from the earlier Jewish teachers. But in Jesus' view to hate your enemy is to contradict the meaning of the command. For Jesus my "neighbour" is anyone I come in contact with and to whom I can show love. The classic picture of this is the parable of the Good Samaritan.
Answer from Peter Kirkpatrick on Stack ExchangeKnowable Word
Context Matters: You Have Heard That it was Said...But I Say to You
July 28, 2018 - And we can, in fact, know what was being said in streets and synagogues, regarding six very specific case studies: “You have heard that it was said…” This formula does not refer to the written scripture but to the oral traditions of the scribes and Pharisees.
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Quora
In the Bible, what is the meaning and difference of 'is written', and 'you have heard it said'? Can you provide examples? - Quora
Answer (1 of 9): "it is written", "we have heard", "I have heard", and "you have heard it is said" is an informal citation that is used in the new testament that might correspond to the portions of the old testament of the bibliography. These phrases were mostly uttered by Jesus Christ to bolster...
Quora
What is the difference between 'it's written' and 'it's said'? - Quora
Answer (1 of 2): We sometimes hear ‘It is written’ when someone quotes a passage from a religious or moral work, e.g., “It is written that everything has beauty, but not everyone sees it.” ‘It’s said’ is used for what the speaker thinks is common knowledge or what the speaker ...
YouVersion
Matthew 5:38-48 “You have heard that it was said, ‘Eye for eye, and tooth for tooth.’ But I tell you, do not resist an evil person. If anyone slaps you on the right cheek, turn to them the other cheek also. And if an “Here’s another old saying that deserves a second look: ‘Eye for eye, tooth for tooth.’ Is that going to get us anywhere? Here’s what I propose: ‘Don’t hit back at all.’ If someone strikes you, stand Ye have heard that it hath been said, An eye for an eye, and a tooth for
Ye have heard that it hath been said, Thou shalt love thy neighbour, and hate thine enemy. But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you; that ye may be the children of your Father ...
Walking With Giants
Matthew 5:21f – “You have heard it said…but I say to you” – Walking With Giants
Jesus looks at several examples of how they had done this, and demonstrates how correct interpretation and application of the Law must be based upon proper intent and motive. Jesus does not say, “Hear what the OT says,” but rather, “You have heard it said.” He is not negating the OT, ...
Bible Study Tools
Matthew 5:37 - All you need to say is simply ‘Yes’ or ‘No’; anyth... | Bible Study Tools
Matthew 5:37 All you need to say is simply ‘Yes’ or ‘No’; anything beyond this comes from the evil one.... Read verse in New International Version
Bible Hub
Matthew 5:38 You have heard that it was said, 'Eye for eye and tooth for tooth.'
You have heard that it was said, 'Eye for eye and tooth for tooth.'
Bryan Hodge
You Have Heard… But I Say | Bryan Hodge
February 17, 2016 - These words are used six times by Jesus in the Sermon on the Mount. Two verses are helpful in interpreting these words. (1) Matthew 5:20, "For I say to you, unless your righteousness exceeds the righteousness of the scribes and Pharisees, you will be no means enter the kingdom of heaven."
An Informed Faith
You have heard it said … but I say to you … (Matt 5; Epiphany 6A)
May 11, 2021 - This Sunday, as we follow the revised common lectionary, we read another section of the teachings of Jesus from the book of origins (Matt 5:21-37) which forms a part of a larger section which is traditionally called the Sermon on the Mount (5:1-7:29). It has this name because it takes place ...
Quora
In Matthew 5, at verse 21, a number of sayings start with the phrase, ...
Answer (1 of 6): He was making a distinction between what the corrupt priests and religious leaders SAID the (Old) Law was… versus what the (Old) Law actually said. The people themselves were supposed read the Law themselves… even delight in it (Deuteronomy 17:8, 9; Joshua 1:8; Psalm 1:2). ...
Bob Yandian Ministries
It Is Written — Bob Yandian Ministries
March 6, 2025 - “As it is written: There is none righteous, no, not one.” (Romans 3:10, Psalm 14:3) This quotation is found in many parts of the Old Testament, the prophets as well as the Psalms. Our verse in Romans 3:10 simply shows God’s word has much to say about itself. But the most important thing
BibleRef.com
What does John 10:34 mean? | BibleRef.com
ESV Jesus answered them, "Is it not written in your Law, ‘I said, you are gods’?
Ligonier Ministries
What Does Matthew 5:17–18 Mean?
Matthew 5:17–18 is a key text for interpreting the Sermon on the Mount and the entire gospel of Matthew: Do not think that I have come to abolish the Law or the
Bible Study Tools
Matthew 5:21 - “You have heard that it was said to the people lon... | Bible Study Tools
Matthew 5:21 “You have heard that it was said to the people long ago, ‘You shall not murder,and anyone who murders will be subject to judgment.’... Read verse in New International Version
Bibletruths
"But I Say Unto You"
Rather than challenging what the Law actually taught, Jesus is refuting what they said the Law taught (see the expression, "…ye have heard it was said by them of old time…," not, "…you have read" or, "it is written," Matt. 5: 21, 27, 31 33, 38, 43, cp.
Unity
Matthew 5:27-28 "You have heard it said ... but I say to you ..." | Unity
Now, however, Jesus is calling ... realize that it is only by changing our thoughts that we can release fear, embrace the true Source of love, and allow that loving energy to create a new and loving life experience. ... “You have heard that it was said, ‘You shall not ...