Matthew 5:34
33 “Again, you have heard that it was said to an older generation, ‘Do not break an oath, but fulfill your vows to the Lord.’ 34 But I say to you, do not take oaths at all—not by heaven, because it is the throne of God, 35 not by earth because it is his footstool, and not by Jerusalem, because it is the city of the great King. 36 Do not take an oath by your head because you are not able to make one hair white or black. 37 Let your word be ‘Yes, yes’ or ‘No, no.’ More than this is from the evil one.
2 Enoch 49:3
Secrets of Enoch1 I assure you, my children, but without any oath, neither by heaven nor by earth, nor by any other creature that God created. 2 The Lord declared: There is no oath in me, only truth, without injustice. 3 If men lack truth, let them affirm or deny with simple words: Yea, yea, or Nay, nay. 4 I assure you with all certainty that before a man exists in his mother's womb, a place is prepared for the repose of his soul, and a measure is fixed for his trials in this world. 5 Do not deceive yourselves, my children, for a place has been prepared for every human soul.
Notes and References
"... In the Jewish tradition the call to truth-telling is also common. The Jewish expert, Montefiore, comments: "I do not think that the 'unbedingte Wahshaftigkeit im Reden' (unqualified truthfulness in speech) which Jesus demanded was not also demanded, and was not also regarded as part of the moral ideal, by the Rabbis.' Examples in Rabbinic literature include Ruth Rabbah 1:6& and Baba Mezia 49a. Finally, there is compelling evidence that 2 Enoch 49:l should not be utilized to support the Jewish oath formulation "yes, yes" since 1) this passage is missing in the shorter recension; 2) the work shows Christian influence; 3) the MSS date only from the 16th and 17th centuries; and 4) the type of swearing which is commanded ("yes, yes" or "no, no") is explicitly stated not to be an oath. Therefore, based upon the close connection of Mt. 5:34a and 37 and the unanimous witness of the early church, it seems best to understand Matthew as passing on Jesus' exhortation to speak the truth without relying upon an oath ..."
Deppe, Dean B. The Sayings of Jesus in the Paraenesis of James (p. 241) Academisch Proefschrift Vrije Universiteit Te Amsterdam, 1990