Interesting observation. Oath. All of us, probably, at least once in their lives vowed in something.
It could be, anytime, anywhere. We swear, friends or entering public office. Swear and witnesses in the testimony of the court. When a man and a woman marry, they also swear allegiance to each other. Even doctors have an oath of Hippocrates. Almost in all aspects of society there are vows.
What is an oath. In most meanings, the word oath is referred to as a solemn promise of something.
Why do we swear. At first I thought that an oath is a promise that is simply not feasible. People decided that offering an oath would help to cement the promise and make a person fulfill it, through effort. But as we know that all vows are broken and the reason is one, everything returns to normal. If you use the definition solemnly, then the oath has the value of publicity and is more like a small show of one actor. With a very serious look, we give a promise, all in a kind of saying that this is important.
And yet, in fact, they promise, when promises cannot be fulfilled. If this were doable, then why swear. But there is no need to fix it with a solemn moment, that was for what to ask. Not only for the very vow, for the words, but for the moment itself. Attract if you need witnesses, and with so many conditions a person will be hard to cope with and maybe he will not be able to give up his oath.
I swear to write only interesting posts!

P.S. do not trust the oaths with one hand, because a person behind his back can cross his fingers and the oath is not valid. as a rule, oath is given with the help of two hands, one of which is raised, and the second is in the vicinity of the heart or the bible, etc.