Again, ye have heard that it hath been said by them of old time, Thou shalt not forswear thyself, but shalt perform unto the Lord thine oaths: But I say unto you, Swear not at all; neither by heaven; for it is God's throne: Nor by the earth; for it is his footstool: neither by Jerusalem; for it is the city of the great King. Neither shalt thou swear by thy head, because thou canst not make one hair white or black. But let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil. (Matthew 5:34-37)

Before the coming of Jesus the Children of Israel were required to make oaths with God. This was such a serious and solemn thing to do that they feared for their life, in both time and eternity, if they broke this oath. This swearing of oaths was a necessary thing in order to keep the worst kind of behavior at bay. But even though they feared breaking the oaths, they were still a disobedient people who sometimes even broke the oaths made to God. But the oaths were made under the authority of the lesser priesthood, the Aaronic, or Levitical priesthood.

The lesser priesthood did not have the keys to salvation. And as a result thereof, any oaths entered into under this Aaronic Priesthood, which were consequently broken, did not have the power of condemnation. Only the breaking of the ordinances of a saving priesthood, the Higher Priesthood, has the power of condemnation.

With Jesus came the Higher Priesthood, or the Melchizedec Priesthood. With this priesthood came the power of salvation and, for the betrayer of the faith; condemnation. Jesus did not want anyone to reap condemnation for any personal weakness that they might later repent from, so, with the Melchizedec Priesthood he removed the taking of oaths, since the making and breaking of oaths under the higher priesthood would place a people under condemnation.

12 But above all things, my brethren, swear not, neither by heaven, neither by the earth, neither by any other oath: but let your yea be yea; and your nay, nay; lest ye fall into condemnation. (James 5:12)

Oaths were replaced by personal covenants with God. Before joining the church through the ordinance of baptism, each candidate were given the opportunity to chose whether or not they would want to serve God, be a witness of Christ, serve their fellow man, and build up the Body of Christ, etc. An authorized representative of the church would ask them if this was the desire of their heart, and in accordance with the teachings of Jesus, they would answer "Yea or nay". Whatsoever is more than these cometh of evil.