Ten percent, and where it comes from is contested — the tithe is an Israelite agricultural and temple institution, and the New Testament never commands it in that form. Most Pentecostal and evangelical churches teach it as binding anyway, mainline churches treat it as an aspiration, and Catholic and Orthodox parishes generally do not use the language at all. It works: it funds a worldwide network of congregations, clergy, schools and relief agencies with no state support, and giving rates among committed evangelicals are measurably higher than among any comparable group. It is also the mechanism prosperity theology runs on — give and it shall be given unto you, preached as a return on investment — which is enormously successful in West Africa, Brazil and the American South and is condemned by most of the rest of the tradition, including by African theologians who have watched it take money from people who have none.