Also, capital appreciation gains (e.g. house value rising), might be a separate category, flowing from Old Testament principle.
Don't want to derail the thread, but I thought this was quite an interesting comment. Could you elaborate on the principles you are thinking of and how they would apply to us today?
Reformed theology helps us here.
The ceremonial law, being fulfilled in Christ, its end, is abrogated.
The civil law given Israel expired with the nation except that equitable principles contained in them may continue.
Moral law (e.g. The Ten Commandments) is perpetual, binding on all men in all generations.
(cf. Westminster Confession of Faith, Chapter XIX, "
Of the Law of God" for a summary of the doctrine of Scripture on the kinds of "law" in Scripture)
Part of the civil law given Israel established various tithes. Remember, that the Levites got their support from the tithe because they were not given "land grants" like the other tribes.
There were tithes on income, the fruit of one's land, the fruit of one's animals, and on increases from year-to-year.
One example:
Deuteronomy 26
12When thou hast made an end of tithing all the tithes of thine increase the third year, which is the year of tithing, and hast given it unto the Levite, the stranger, the fatherless, and the widow, that they may eat within thy gates, and be filled;
(see also Deuteronomy 14 generally)
The principle being that a capital increase, a real value increase from year-to-year is also a basis for the tithe.
Remember, the tithe, the ten percent, of each of these kinds is NOT strictly binding on us today, as it was on the Old Testament theocracy of Israel.
That nation was constituted by God, uniquely, with 11 of 12 tribes receiving land grants and the 12th, Levites receiving their support through tithes because they could not own land.
That's only one aspect of how the Old Testament theocracy of Israel was different than any other nation.
But, there are principles that apply:
1) God gets a "first portion"
2) on everything we possess (including increased value)
3) 10% was the least amount He ever asked for in the Old Testament