Tithing is an Old Testament concept. The tithe was a requirement of the law in which all Israelites were to give 10 percent of everything they earned and grew to the Tabernacle/Temple.
In fact, the Old Testament Law required multiple tithes which would have pushed the total to around 23.3 percent, not the 10 percent which is generally considered the tithe amount today. Some understand the Old Testament tithe as a method of taxation to provide for the needs of the priests and Levites in the sacrificial system. The New Testament nowhere commands, or even recommends, that Christians submit to a legalistic tithe system.
The New Testament nowhere designates a percentage of income a person should set aside, but only says it is to be “in keeping with income” (1 Corinthians 16:2). Some in the Christian church have taken the 10 percent figure from the Old Testament tithe and applied it as a “recommended minimum” for Christians in their giving.
More details here for you 10 percenters!
ps. Some "Christian" groups are already urging a boycott!