“What is the theological basis for tithe in Christendom?”
This is a very good question. There are some who believe that tithing ended at the time of Christ, and that Christians are not obligated to pay tithes. Is this what the Bible says? Jesus said, “Woe unto you, scribes and Pharisees, hypocrites! for ye pay tithe of mint and anise and cummin, and have omitted the weightier matters of the law, judgment, mercy, and faith: these ought ye to have done, and not to leave the other undone.” (Matthew 23:23) According to Jesus we should not leave paying tithe undone.
When Jesus sent forth workers into the ministry He said, “Carry neither purse, nor scrip… And in the same house remain, eating and drinking such things as they give: for the labourer is worthy of his hire.” (Luke 10:4, 7) Jesus intended from the beginning for the ministry of the gospel to be supported by tithes and offerings. He could miraculously withhold 10% of our income but, instead, He allows us to have a part in this as a way to eradicate selfishness and keep before our minds the fact that God owns all things. Paul wrote,
“Who goeth a warfare any time at his own charges? who planteth a vineyard, and eateth not of the fruit thereof? or who feedeth a flock, and eateth not of the milk of the flock? Say I these things as a man? or saith not the law the same also? For it is written in the law of Moses, Thou shalt not muzzle the mouth of the ox that treadeth out the corn. Doth God take care for oxen? Or saith he it altogether for our sakes? For our sakes, no doubt, this is written: that he that ploweth should plow in hope; and that he that thresheth in hope should be partaker of his hope. If we have sown unto you spiritual things, is it a great thing if we shall reap your carnal things? If others be partakers of this power over you, are not we rather? Nevertheless we have not used this power; but suffer all things, lest we should hinder the gospel of Christ. Do ye not know that they which minister about holy things live of the things of the temple? and they which wait at the altar are partakers with the altar? Even so hath the Lord ordained that they which preach the gospel should live of the gospel.” (1 Corinthians 9:7-14)
Peter and the other apostles said, “We will give ourselves continually to prayer, and to the ministry of the word.” (Acts 6:4) The apostles could not have done this if they had to continually support themselves and their families without the support of tithes and offerings.
The work of the ministry has always been supported by the tithes and offerings of God’s people. If God had intended for it to be otherwise, He would have told us. God said, “Will a man rob God? Yet ye have robbed me. But ye say, Wherein have we robbed thee? In tithes and offerings. Ye are cursed with a curse: for ye have robbed me, even this whole nation. Bring ye all the tithes into the storehouse, that there may be meat in mine house, and prove me now herewith, saith the LORD of hosts, if I will not open you the windows of heaven, and pour you out a blessing, that there shall not be room enough to receive it.” (Malachi 3:8-10) It is a serious thing to rob God, yet God says that is what we do if we neglect to return tithes and give offerings. God promises that if we do this He will open the windows of heaven and pour out blessings beyond what we can receive. If God had changed His mind about this, He would have informed us somewhere in the Bible, but there is no hint anywhere that tithing has been done away with. Tithing is still required by God. The tithe is to be returned on our increase, whether it be in our garden, at our job, or a gift from others.
I hope this helps to answer your question.