I am not suggesting that Abraham was a dirty old man. Only that when it came to making a serious oath with someone, he preferred a hand under his thigh rather than a handshake. For instance, when Abraham implores an elder servant to make a pledge by Jehovah God he says:
“Put I pray thy hand under my thigh.” (Genesis 24:2)
According to theologian Emanuel Swedenborg, it was an ancient custom to do such a thing when someone was making a solemn oath to another. This custom was based on a special symbolism in which the various parts of the human body represented psycho-spiritual values.
Hands represent power and ability, because one’s power and ability is directed towards the muscles of the hands. So when two people give a handshake they are communicating a willingness of friendship and making agreement to the best of their ability and power of their understanding (hands like the human intellect “grasps” things).
The thigh is in close proximity to the genitals and represents the prolific power of love. So any reference to the thigh brings in a whole new dynamic to an oath or pledge.
Whereas shaking hands represents an intellectual agreement, a hand under the thigh signifies a much deeper agreement—a pledge between the understanding and genuine goodness or between love and wisdom. In other words, it is a spiritual pledge, made by a person’s soul not only to another person, but to God. It is similar to the more modern custom of putting one’s hand’s on the Bible in a courtroom and pledging to tell the truth.
It is a pledge made by an agreement and union between the heart and mind.
Every part of the biblical story of Abraham asking his servant to make an oath to find the proper wife for Isaac contains these deeper symbolic meanings that communicate greater details about doctrine and faith than can ever be obtained by a mere literal interpretation of its words.
Above the literal meanings of the biblical narratives there are two distinct levels of higher symbolic meaning. On the first higher level, the story of Abraham and his servant represents the creation of a new church through new God-given directives that seek to arrange (regenerate) the ideas of the human psyche to serve a higher master.
On the highest level, the story of Abraham represents the process of glorification that the Lord underwent while in the world. If every word in Scripture did not ultimately refer to hidden details of the Lord’s life, He could not have “made the Word flesh” nor could Scripture have a rational basis for its sanctity.