Tithing is a biblical principle. In Malachi 3:10, the bible talks about giving our first and our best back to God, and He will bless the rest. A tithe is giving 10% of your income and trusting God to provide abundantly for you and your family when you put Him first in your finances.
"Bring the whole tithe into the storehouse, that there may be food in my house. Test me in this,” says the Lord Almighty, “and see if I will not throw open the floodgates of heaven and pour out so much blessing that there will not be room enough to store it." Malachi 3:10 NIV