These passages contain unpopular but straightforward teaching, along with some possible depth that we may be missing as later readers that are not familiar with the Law of Moses in the same way Jesus’ listeners were. Jesus continues to highlight the differences between his disciples and the Pharisees.
Matthew 5 : 31 – 37
“It has been said, ‘Anyone who divorces his wife must give her a certificate of divorce.’ But I tell you that anyone who divorces his wife, except for marital unfaithfulness, causes her to become an adulteress, and anyone who marries the divorced woman commits adultery.
“Again, you have heard that it was said to the people long ago, ‘Do not break your oath, but keep the oaths you have made to the Lord.’ But I tell you, Do not swear at all: either by heaven, for it is God’s throne; or by the earth, for it is his footstool; or by Jerusalem, for it is the city of the Great King. And do not swear by your head, for you cannot make even one hair white or black. Simply let your ‘Yes’ be ‘Yes,’ and your ‘No,’ ‘No’; anything beyond this comes from the evil one.”
New International Version, 1984 Edition