Should Christians tithe? Here's what I know.
It seems clear from Scripture that tithing was not taught to the Church. Reading through the New Testament letters and Acts we can see that tithing is not mentioned to the Church.
Further, the chapters on giving in 2 Cor. 8 and 9, where Paul says it's not to be compulsory and that it involves equality—both giving and taking—show that there's a mindset different from tithing.
The only quotes addressing "should Christians tithe" in the 2nd century—leaving out the ones that sort of 'accidentally' mention it by quoting Scriptures with the word tithe in them—are:
One history book I read said that tithes came back under the reign of Pepin the Short among the Franks in the 8th century. It was reintroduced to support the monks.
I don't remember which book I read that in, and I haven't followed it up due to the position of the New Testament and the early Christians being so clear.
There's a couple more quotes that I've put up on the Giving Quotes page. The idea seemed clear to the early Christians that we share everything together, not that we tithe. Collections were taken, say Justin and Tertullian, but they were completely free will. No mention of tithing is made. (Justin, First Apology 67; Tertullian, Apology 39).