WASHINGTON — LaVonne and Bernard Snowden have three children in private school, two flourishing careers and an elegant house in Mitchellville, Md. As thanks for those blessings, the Snowdens say, they give 10 percent of everything they make to their church.

Carla Brooks, a Howard University graduate student, doesn't bring in much except her financial aid and what she earns working part time. Even so, she puts 10 percent of her money in an envelope marked "tithes."

"Anything that I get, I tithe," Brooks said. "It's not a hardship at all. It's like when anyone else gets their check. They see what they have, they pay their bills and live on what is left. I tithe, and I live off the rest."

Tithing, an ancient practice described in the Bible, is particularly strong in African-American communities, where it is reinforced by centuries of family tradition. That has helped propel Prince George's County, Md., into the top five counties in the nation for charitable giving, as documented by a Chronicle of Philanthropy study based on donations as a percentage of income.

An analysis of that data found that 14 of the top 20 ZIP codes for per-capita giving in the region were in Prince George's.

Across the spectrum of faiths, religious institutions draw much of the nation's charitable money, accounting for $3 out of every $4 given, the chronicle's study of 2002 IRS data found. In African-American communities, it's closer to $9 out of every $10.

When the Rev. Jonathan Weaver arrived at Greater Mount Nebo African Methodist Episcopal Church 18 years ago, his congregation had 65 members, and fewer than 1 percent tithed. The congregation in Bowie, Md., has grown to more than 2,000 members, they worship in a $4.6 million sanctuary, and more than 75 percent tithe, Weaver said.

"Some people have a sense that pastors are heavy-handed ... in the use of the Scripture to insist that people tithe," he said. "But we are not encouraging people to give 10 percent. We want them to be effective managers of the other 90 percent. God wants us to be effective managers of what he has entrusted us with."

At some churches, tithing is the backbone of a movement known as "prosperity ministry," through which churchgoers are encouraged to give under the belief that they could receive riches in return. The Rev. C. Matthew Hudson Jr., pastor at Matthews Memorial Baptist Church in southeast Washington, D.C., has been delivering a 12-week series of sermons encouraging churchgoers to put in not just the traditional 10 percent but even more to support their church.

"God is a promise keeper," he said. "He says if you give (to) me, try me and see if I won't open a window from heaven and pour you out a blessing. I'm going to bless your health, family finances and future."

Tithing first appears in the book of Genesis (Abraham gave "a tenth" to Melchizedek, king of Salem) and references to the practice are sprinkled throughout the Old Testament.

In modern times, the practice is open to many interpretations. Should a family give 10 percent of all its income, or of just one salary? Before or after taxes? To the local church or broader ministries?

Many churches of various denominations emphasize gifts of "time, talent and treasure," allowing some members to meet their biblical obligation with volunteer hours or other services.

One of the five pillars of Islam is zakat, which calls for contributing 2.5 percent of income. In the Jewish faith, the tradition of tzedakah focuses on "giving to be just or right" and not on meeting a specific goal for giving, said Rabbi Fred Reiner of Temple Sinai in northwest Washington, D.C.

Kenneth Page, stake president of the Church of Jesus Christ of Latter-day Saints churches in the District of Columbia and in southern Maryland, said Mormons must tithe 10 percent of their "increase." The church lets individuals decide whether to tithe gross or net income.

Of the 4,500 members in the 12 churches that Page's stake includes, about 50 percent tithe at least 10 percent and an additional 25 percent give something above a regular offering. Page said tithing is considered a commandment just as much as not stealing and not lying are.

The Rev. Granger Browning of Ebenezer A.M.E. Church in Fort Washington, Md., said about 70 percent of his 15,000 members tithe, in part because they can see the good work the church is doing for the homeless, poor and addicted in the community.

"If you can convince them of a need, persons are very generous — even those who are not wealthy," Browning said. "Especially older persons, senior citizens. They will always give to churches, and that has helped as the churches have been called to give as the government cuts back on some services."

But that view of tithing — as biblical obligation and community service — has given way in some churches to an emphasis on giving under the belief that the members will prosper financially in return.

"What we are seeing is more giving, but I wouldn't attribute it only to people adhering to the principle of tithing," said the Rev. Bucas Sterling, pastor of Kettering Baptist Church in Upper Marlboro, Md. "There is also an increase in what is called 'prosperity ministry,' the approach that says the intention of God is for all of his children to be financially well off. Materialism is being promoted, in a way. The whole idea is that God wants them to have money.

"The hook that this ministry is promoting is that you must give a lot to receive a lot. You put money in, you get money out. Almost like an investment, whereas the principle of tithing is that you should give to be obedient to God."

Such an emphasis on individual enrichment and empowerment, as described by Dallas minister T.D. Jakes, has allowed the church to abandon its emphasis on community and political advocacy, some ministers say. Others worry that the perception of clergy growing rich on the proceeds of their ministry could alienate churchgoers.

Deloris Walker of southeast Washington, D.C., gives her 10 percent at Hudson's church. Walker, a Department of Agriculture secretary, said tithing proved a hardship initially, but she was determined to make the sacrifice.

"I never made enough money to tithe, but my blessings became more abundant when I started," she said. "Things just seemed to happen in a positive way. Since I started tithing, my financial situation is much better, and I have been blessed even more."

Washington Post staff writer Hamil R. Harris and staff researcher Derek Willis contributed to this report.