Adventists believe tithing is a biblical requirement.
They also believe that the 10 Commandments are the law of God, and the rest is the law of Moses, but keep parts of the law of Moses and discard the parts they deem unnecessary. They differentiate between a moral law (the 10 commandments, including the ceremonial aspects of it) and a ceremonial law (which includes the moral laws outside the 10 commandments) but keep the ceremonial laws of Moses they deem to be health-related (even if they aren’t health related at all.)
Very confusing for them. Anyway, Dave Armstrong has a lovely explanation as to where tithing really fits into the Christian worldview. Read it on his blog here:
Biblical Evidence Against Tithing … by Dave Armstrong