We have to give regularly give proportionately in the NT and tithing is a general equity principle from the ceremonial law and from the patriarchal period which guides us in what kind of proportion is suitable.
On the first day of every week, each of you is to put something aside and store it up, as he may prosper, so that there will be no collecting when I come (I Corinthians 16:2).
We have to learn and teach about principles of general equity from the OT.