It is important to remember that in this section of the Sermon on the Mount Jesus expounds on the meaning of his command, “unless your righteousness surpasses that of the scribes and Pharisees, you will not enter the kingdom of heaven.”
In this text, “Jesus used the phrase ‘You have heard that the ancients were told,’ or a similar one, to introduce each of the six corrective illustrations He gives in this part of His sermon (see vv. 21, 27, 31, 33, 38, 43).
The phrase has reference to rabbinical, traditional teaching, and in each illustration, Jesus contrasts that human teaching with the divine Word of God.
[John MacArthur, /MacArthur's New Testament Commentary: Matthew 1-7/ (Copyright © 1985 by The Moody Bible Institute of Chicago Electronic Edition STEP Files Copyright © 1997, Parsons Technology, Inc), Chapter 26]
Daniel Webster wrote, “There is nothing as powerful as truth and often nothing as strange.”
The Jews of Jesus’ day revered the idea of truth in principle, but in practice it was buried under their system of tradition, which over the centuries had continually cut God’s law down to fit their own sinful perspectives and purposes.
In Matthew 5:33-37 the Lord proceeds to expose their convenient distortion and contradiction of the divine revelation they claimed to love and teach.
We will look at this text under two headings, a practice examined and a principle emphasized.
A Practice Examined (5:33)
The law of Moses
Those exact words are not found in the OT but are derived from three verses.
Leviticus 19:12 “You shall not swear falsely by My name, so as to profane the name of your God; I am the LORD.”
Numbers 30:2 "If a man makes a vow to the LORD, or takes an oath to bind himself with a binding obligation, he shall not violate his word; he shall do according to all that proceeds out of his mouth.”
Deuteronomy 23:21 "When you make a vow to the LORD your God, you shall not delay to pay it, for it would be sin in you, and the LORD your God will surely require it of you.”
The purpose of these commands…
Ø Was to bridle man’s sinful tendency to lie.
Ø Was to restrict oath-taking to serious matters.
God provided for proper oath-giving in His name as an accommodation to sinful human nature.
Hebrews 6:16 “For men swear by one greater /than /themselves, and with them an oath /given /as confirmation is an end of every dispute.”
These facts are proof that Jesus was not dealing with the Mosaic Law but with the Pharisaical perversion of it.
The legalism of the Pharisees
The tradition Jesus mentions in verse 33 seemed to be biblical, but it had several flaws that made it fall short of what the Old Testament actually taught.
The Pharisees were more concerned about the letter of the law than the spirit of the law.