Jesus teaching on this topic is from Matthew 5:33-37. He says,

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.’  34 But I say to you, do not swear at all: neither by heaven, for it is God’s throne;  35 nor by the earth, for it is His footstool; nor by Jerusalem, for it is the city of the great King.  36 Nor shall you swear by your head, because you cannot make one hair white or black.  37 But let your ‘Yes’ be ‘Yes,’ and your ‘No,’ ‘No.’ For whatever is more than these is from the evil one.

As D. Martyn Lloyd-Jones points out in his book, Studies In The Sermon On The Mount, the teaching of the Pharisees on the subject of oaths, from verse 33, “…are not to be…