That a side, there is one interesting way of swearing noted by Skeptic's Annotated Bible: verse 2 "Put, I pray thee, thy hand under my thigh:". What does it mean to "put you hand under my thigh"?
A bit of googling...
from YAREK OATH, CIRCUMCISION, GOD'S INNER THIGH, KNEELING & PRAYING HANDS
Genesis contains passages in which a male takes an oath by placing his hand “under the thigh” of the male to whom he is swearing. It has sometimes been interpreted as swearing upon, or touching, the testicles.
That's what I was reading and trying to find out ...
The Hebrew word in some passages is ‘yarek,’ meaning ‘thigh’ in the Old Testament. That ritual might derive from the belief that the thigh is a center of power, probably because it is near the genitals. Some interpreters argue that it is a swearing upon the genitals, with "under the thigh" being a euphemism in Hebrew.
Dr. Lee Stone, in his book “The Power of a Symbol,” said that the “most ancient way of administering the oath was by placing the hand between the thighs, on the genitals. These were regarded as the Christian and the Jew regard the Bible, as being the most sacred of tangible things” (10, pg. 45).
Dr. P. C. Remondino, in his book “History of Circumcision from the Earliest Times to the Present” said that “It was partly this custom of swearing, or of affirming, with the hand under the thigh, by the early Israelites,” which led many to believe that their hand was being placed on the testicles (11, pg. 35).
It is likely that the passages above inspired the popular claim that the word ‘testify’ derived from ‘testicle,” but the claim is disputed with alternative derivations and interpretations.
A popular claim also alleges that Greeks and Romans would touch their own testicles while swearing, however there is no evidence in support. The "testicle" theory argues that the testicles were used for oaths because they represented virility, power, and represented the man’s future generations, and the source of life.