Should a Christian pay tithes?

The tithe is clearly taught in the Old Testament, but in the New Testament it seems to be downplayed. Are those of us who give 10 percent of our income doing something not required?
 

We know that the law of Moses mandated the tithe (see Lev. 27:30-33), at least in part to support the ministry of the Levites (Num. 18:21-24). Like many other laws, however, it was frequently observed in the breach, although the prophets insisted that failure to pay the tithe was nothing less than robbing God (Mal. 3:6-12).

There were also offerings to be paid. Moreover, faithful Israelites were to be generous with their alms, so that the poor of the land were supported.

In practice, the prophets found themselves inveighing against greed and social injustice (e.g., Amos) and against a raw form of capitalism that squeezed out the poor (Isa. 5:8-10). In other words, even within the Old Testament we should be careful not to isolate the tithe from broader demands of generosity and social justice.

The only passage in the New Testament that explicitly authorizes the tithe does so in a rather backhanded way: "Woe to you, teachers of the law and Pharisees, you hypocrites! You give a tenth of your spices. … But you have neglected the more important matters of the law—justice, mercy, and faithfulness. You should have practiced the latter, without neglecting the former" (Matt. 23:23, NIV).