So the reason the tithe is not commanded by Paul is not that Jesus abolished it. He didn't, He approved it (Lk. 11:42). Nor was the reason that we should no longer give proportionately. We should “as we may prosper” (1 Cor. 16:2). The more you make the more you give. Nor was it that the need of the ministry is less in the New Testament. It's not. Teaching, preaching, caring and missions all take money… The reason that Paul did not use the command to tithe in order to enforce his teaching about giving was that he wanted to emphasize willingness over constraint, and liberality over limitation, and a sense that all our money is God's not just a tenth.