Abraham is the struggling self climbing toward God, and the tenth part he yields is the portion the lower man renders up to the higher order within him. The king he pays is named twice by root: King of righteousness, the right hemisphere of the brain where the higher order rules, and King of Salem, the salt and the electron, the electromagnetic peace that settles when that higher faculty governs. The names open into the body, one giving the ruling side of the mind, the other giving the charged stillness it brings.
So the striving self hands a measured share of all it has to the higher king seated in the right side of the head, and the reward is the electric calm the name Salem carries. The exchange is not tribute to a priest but the lower nature yielding to the ruling mind and receiving its peace.
Abraham: the struggling self rising toward God, the lower man on his climb
King: the higher self, the ruling faculty seated within
Righteousness: the right hemisphere of the brain, the higher order that governs
Salem: salt and the electron, electromagnetism, the charged peace of the settled mind