This is the source from the bible for the law, that a person must hold a holy object when making an oath, similar to a holy Torah, written on parchment. However according to the law, this type of oath is only made when a person admits partially to a claim but not when he denies the claim entirely.
The legal reason for this rule is the following. When someone denies the entire claim, he is either telling the truth or he is so brazen that making an oath will not help prove anything. Either way, there is no need or benefit from making an oath. While someone who admits partially, demonstrates a degree of conscientiousness and accountability, therefore we say an oath will certainly help push this kind of person to the absolute truth if needed.
All laws have a spiritual equivalent within the life and soul of each individual.
G-d loans and provides every human being with a living soul, with which the person is able to do and to accomplish all that he does while he is alive. Every person is indebted and obliged to G-d and has the responsibility to not only return the soul as granted, clean and pure, he is also expected to use this potential for achieving and accomplishing, in an appropriate G-dly way.
Sometimes it can happen, that a person admits only partially to this fact of truth. He recognizes, that G-d is the ultimate supreme ruler from which everything emanates, and that G-d grants all that he has, but he is only doing this partially. He doesn’t admit, that ALL is from G-d and therefore in ALL areas of life G-d must be considered. It may seem to a person that in certain areas of his life, what he has and what he is, is really the results of his prowess and wisdom. A “self made” man or woman, and it is he – or she, who takes the credit or even the blame for the results and therefore in those areas, G-d is out of the picture.
Sure, he prays and does whatever he can to be G-dly. But he says to himself, c’mon, we need to be a little “realistic”, if not for me, it would never happen.
We’re not talking about someone who denies G-d entirely. Most people recognize, and are aware, that they could never do it all on their own. Just like a person does not bring himself into being. There has to be a source for the world, which created and brought this universe into being. The world did not and can not possibly bring itself into being.
So what’s the advice we recommend for the partial denier; an oath.
In Hebrew the word for oath literally can also mean, to supply and to indulge. Just like a satisfied and gratified person has more, the idea of an oath spiritually is to push the person over the top and grant him with just a little bit more strength, to help him recognize, that even in the small details, ALL is from G-d, which forces him to feel the full indebtedness he owes and must pay to G-d.
Just like when making an oath, the strength to acknowledge the truth, comes from the requirement to hold a Holy object, the same is also spiritually. The only way a person will fully admit and recognize the credit to his existence as being ALL to G-ds credit, is by holding on to holy thoughts, study and G-dly practices whenever possible. The steady attachment and connection to G-dly input keeps the person in check.