Can you put a price on faith? That is the question churchgoers are asking as the tradition of tithing — giving 10 percent of your income to the church — is increasingly challenged.

Opponents of tithing say it is a misreading of the Bible, a practice created by man, not God. They say they should be free to donate whatever amount they choose, and they are arguing with pastors, writing letters and quitting congregations in protest.

In response, some pastors have changed their teaching and rejected what has been a favored form of fund raising for decades. The backlash comes as some churches step up their efforts to encourage tithing. Some are setting up "giving kiosks" that allow congregants to donate using their debit cards when they attend services. Others are offering financial seminars that teach people in debt how they can continue tithing even while paying off their loans. Media-savvy pastors, such as Ed Young in Grapevine, Texas, sell sermons online about tithing.

Church leaders say tithing isn't just a theological issue, but a financial one. Americans gave an estimated $97 billion to congregations in 2006, almost a third of the country's $295 billion in charitable donations, according to Giving USA Foundation, a nonprofit educational organization in Glenview, Ill. But giving to religion is growing more slowly than other types of giving, says Patrick Rooney, director of research at the Center on Philanthropy at Indiana University. That's partly because people are attending church less frequently, says Mr. Rooney, and are giving to a wider array of causes, including secular ones. That worries some church leaders. "If everyone gives 2 percent of their income because that's what they feel like giving, you aren't going to have money to pay the light bill and keep the doors open," says Duane Rice, an official with Evangelical Friends International, a denomination that believes that tithing is required by the Bible.

Many Christians who don't read the Bible literally say that by tithing they are not misreading the text, but rather interpreting it differently. Tithing has its roots in the Biblical tale of Abraham presenting a tenth of the war spoils to Melchizedek, the king of Salem. In the Old Testament, Jews brought 10 percent of their harvest to a storehouse as a welfare plan for the needy or in case of famine. That percentage, say pro-tithers, can be a useful guideline for Christians today. "It's the best financial discipline I know," says Terry Parsons, stewardship officer for the Episcopal Church.

Other faiths also urge followers to donate. Muslims are obligated to give a zakat to charity, usually 2.5 percent of the market value of a believer's assets each year. Most Jewish synagogues request an annual membership fee, often based on family income.Tithing ranges from a requirement to a suggestion, depending on the denomination and the church. LDS faithful are asked to give 10 percent to the church or they may be restricted from participating in certain sacred ceremonies. Some evangelical Protestant churches require new members to sign covenants, promising to tithe or give generously. Those who openly refuse to tithe might be denied leadership roles or asked to leave the congregation.

For Judy Willingham, of San Antonio, 12 years of tithing came to an end earlier this year. She says she gave a tenth of her pay to Cornerstone Church because the pastor, the Rev. John C. Hagee teaches, "'If you obey God and you tithe, God will return it to you 30, 60, 100 fold."'

Willingham, who earns $26,000 annually as an administrative assistant, says she started to research the practice, reading criticism online and studying the Bible, and concluded that she'd been "guilted into tithing." She quit the church and hasn't found another one.

Steve Sorensen, director of pastoral ministries at Cornerstone, says the church requires its paid and volunteer leaders to tithe, and teaches new members to do so, although it doesn't make them show proof of income. "When you tithe, God makes promises to us, that he ... is not going to let anything bad or destructive come about," says Mr. Sorensen. For those who don't tithe, he says the Lord "is not obligated to do those things for you." Resistance to tithing has been increasing steadily in recent years, as more churchgoers have questioned the way their churches spend money. Like other philanthropists today, religious givers want to see exactly how their donations are being used. In some cases, the growth of megachurches, some with expensive worship center's equipped with coffee bars and widescreen TVs, have turned people off of tithing. And those who object are finding like-minded souls on the Web in theological forums.

Many churchgoers also balk at the idea that a certain amount of money will ensure salvation. They see tithing and say, "no, that's not the way God works," says James Hudnut-Beumler, dean of Vanderbilt University's divinity school and author of the recent book "In Pursuit of the Almighty's Dollar," a history of Protestant fund raising.

John Magrino, a New Jersey lawyer, says he regularly donated money during the weekly collection at his Catholic church, but tithing was a different story. "It's my money to do with what I want," says Mr. Magrino, 39, a father of two. He says he felt guilty when the pastor at Sacred Heart Church in Suffern, N.Y., started giving sermons about tithing and putting reminders in the church bulletin: "That was the message I got from tithing: Make it hurt ... if it hurts, then you get the spiritual renewal." Msgr. Joseph Giandurco, now the pastor at Sacred Heart, says he doesn't ask for tithes, partly because he sensed his congregants disliked it.

Some Baptist churches are trying to encourage tithing by accepting credit-card payments and automatic deductions from checking accounts. Two years ago, the Rev. Marty Baker, pastor of Stevens Creek Church in Augusta, Ga., created the "giving kiosk" machine that allows congregants to donate at the church from their bank cards. He and his wife launched SecureGive, a for-profit company, which has placed 50 kiosks in churches. He says the machines can help track which families are giving the most.

In Gainesville, Ga., Crown Financial Ministries offers training courses to people who then teach churchgoers around the country about how they can save, budget and get out of debt — while still giving 10 percent of their earnings to the church. "When they obey His word, that is to give, God creates opportunities supernaturally for them to save more and spend less," says the Rev. Rob Peters, who began offering Crown classes at First Baptist at Weston in Weston, Fla., five years ago. He says giving to the church rose 31 percent the first year the classes were taught compared with the year before.

When he objected to his church's instructions to tithe, Kirk Cesaretti took it up with the church leaders. In response, he received a letter from the pastor and elders of Hydesville Community Church in Hydesville, Calif. "At this time, we believe your concerns do not warrant any change in our church policy or positions," the letter read.

The letter closed with a verse from Hebrews 13:17: "Obey your leaders, and submit to them; for they keep watch over your souls; as those who will give an account. Let them do this with joy and not with grief, for this would be unprofitable for you."

Mr. Cesaretti, an engineer in Fortuna, Calif., says he took the letter to mean he was no longer welcome at the church. Hydesville's senior pastor, Michael Delamarian III, says he believes "the more you give the more you're going to be blessed." He says he did not bar Mr. Cesaretti from the church.

The anti-tithing movement has found support in some unlikely places: theologically conservative divinity schools and church pulpits. At Southeastern Baptist Theological Seminary in Wake Forest, N.C., professor Andreas Kostenberger challenges tithing in classes on the New Testament. He teaches that if you add up all taxes paid by the ancient Israelites, they exceed 10 percent, and that in the New Testament there's no percentage rule. He says pastors perpetuate the 10 percent figure out of "pragmatism, tradition and ignorance, quite frankly."

After 25 years leading Union Missionary Baptist Church in Chesapeake, Ohio, the Rev. Bob Barbour stopped preaching about tithing a few years ago. He now promotes what he calls "grace giving" — a voluntary, unspecified amount — because, he says, it squares better with Scripture. The church still receives enough to cover expenses, he says. And if it falls short, so be it: "You can't beat people over the heads."

During a staff discussion two years ago about the $2.8 million annual budget, the pastor, the Rev. Mark Engel, said that he expected employees to give 10 percent of their gross income to the church and to teach congregants to do the same. The denomination, an offshoot of the Quaker faith, has long urged members to tithe.

Employee Kevin Rohr earned $32,400 a year organizing activities for young adults, and had a wife and four children to support. He told the pastor in a letter that Christians are not required to tithe. Within months, he quit his job. Mr. Engel declined to discuss the details of Mr. Rohr's employment, but said, "The expectation is that every member of the staff should fulfill the commitment they made to preach and practice the doctrines" of the denomination.

Mr. Rohr, 35, is now supporting his family by driving trucks. He says he still believes what he wrote to Mr. Engel: "All decisions to give and how much to give are between the believer and their God, not meant to be used as stumbling blocks or judgments against others."