(RNS) For some 400 years, the small Reformed Church in America has relied on only three confessional statements of belief, all of them forged in the crucible of the Reformation.

This week, they’ll add a fourth, and its unlikely origins — apartheid-era South Africa — speak volumes about the changing nature of global Christianity and its impact on one of America’s oldest denominations.

On Thursday (June 10), the church will formally accept the Belhar Confession at the church’s General Synod held at Northwestern College in Orange City, Iowa. The confession is a declaration of unity, justice and reconciliation that was written by Reformed churches in the Cape Town suburb of Belhar, South Africa, in 1982.

“It is historic and it adds a needed component to the confessions, the social dimension,” said Mitch Kinsinger, a religion professor at RCA-affiliated Northwestern College.

“For a denomination that has been historically Dutch and white, it opens the windows to a broader sense of what this church is and what it should be.”

The document instructs people to “love one another; that we experience, practice and pursue community with one another; that we are obliged to give ourselves willingly and joyfully to be of benefit and blessing to one another.”

The adoption of this South African document is an important landmark for the RCA, said the Rev. Harold Delhagen, the executive of the RCA’s Albany (N.Y.) Synod.

“This is a recognition that we absolutely have to listen to the voices of the rest of the church,” Delhagen said. “We are just so delighted that the first new confession we adopt comes from the Southern Hemisphere.”

The most vibrant and growing sectors of Christianity are in the so-called “Global South.” By 2100, the Center for the Study of Global Christianity at Gordon-Conwell Theological Seminary estimates that the 2.8 billion Christians south of the equator will be more than triple the 775 million in the north.

Since its founding in 1628, the RCA has relied on three ancient statements of faith — the Heidelberg Catechism, Belgic Confession and Canons of Dort.

The RCA “received” Belhar from the Uniting Reformed Church in Southern Africa in 1995, and has studied it ever since.

In March, two-thirds of the RCA’s 46 classis, or regional bodies, voted to officially add Belhar as their fourth foundational statement of belief. The Christian Reformed Church and the Presbyterian Church (USA) are also considering adopting the statement.

“This is a way to ground our commitment to justice and to reconciliation and to unity,” said the RCA’s general secretary, the Rev. Wes Granberg-Michaelson said. “This means that every theological student will be shaping their faith in light of not only the Heidelberg, the Belgic and the Canons of Dort, but also the Belhar Confession.”

With a little more than 150,000 members in the United States, the RCA is the oldest Protestant denomination with a continuous ministry in North America, according to the 2010 Yearbook of American and Canadian Churches.

Officially adopting the Belhar statement will be the first order of business at this year’s Synod, Granberg-Michaelson said, but he hopes the impact of the document doesn’t end there.

“We’re really giving a confessional foundation to our future,” he said.