Before there were Jews, before there were theocracies, before there were any tablets, before there were priests, before their were Levitical institutions, before there were....(well you get the point)...Abraham willingly gave a tithe to the representative of God Most High. He even partook of a type of communion with him. Abraham is the father of our faith, which, everywhere, even for a Dispensationalist, is all over the NT. Be like Abraham, have faith like Abraham - tithe to the representatives of God Most High. That about settles it In my humble opinion.