These two opinions of Tithing are well worth reading:
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Luther. Martin (Sermon; August 27, 1525): (tithing) [P139]
“But the other commandments of Moses, which are not [implanted in all men] by nature, the Gentiles do not hold. Nor do these pertain to the Gentiles, such as the tithe..."
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MacArthur, John [p54], (tithing) , pp53-54] God's Plan for Giving, Moody Press, 1985 Mega-successful church builder, college founder, author, TV ministry.
"So when someone says the Jew gave ten percent, that isn't true. The Jew gave twenty-three percent to begin with. It was for the poor people, the widows, and people who didn't have anything to eat. So they were funding the people who ran the government, which were the Levites; they were providing for national feasts through the festival tithe; and they gave for the welfare program. All this was funding for the national entity. All three of these were taxation, not freewill giving to God. Tithing was always taxation so that the programs of the government could run: the priestly program, the national religious program, and the welfare program" 76.
Commentary on the Book of Romans 9-16 (p.233)
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Christians are not under obligation to give a specified amount to the work of their heavenly Father. In none of their forms do the tithe or other Old Testament levies apply to Christians.
Thoughts On Tithing (from sermon preached at Grace Community Church in Panorama City, CA):
Tithing, basically, is never, ever advocated in the New Testament; it is never taught in the New Testament-never!

Malachi 3:8