The Bay Psalm Book was a new translation of the Book of Psalms by a group of prominent Puritan ministers. It was an instant hit: Congregations across the Massachusetts Bay Colony were soon singing from the new psalter during worship.

This Sunday, members of Old South Church, which owns two of 11 surviving first-edition copies, are scheduled to vote on a controversial proposal to let its trustees sell one of the books, along with a valuable collection of Colonial-era silver, to help pay for repairs and assure a more financially sound future.

The psalm book alone could fetch an estimated $10 million to $20 million at auction, according to David Redden, vice chairman at Sotheby’s, who called the psalm book “the Gutenberg Bible of America.” It would be the first opportunity for a collector to buy one since 1947.

A number of historic mainline churches have sold off communion silver and other assets in recent years to help their small congregations maintain aging buildings. Earlier this year, First Parish Church in Dorchester sold its silver collection for just over $1.7 million to help pay for a major restoration.

The Rev. Nancy Taylor, senior minister of Old South, described her congregation’s proposed sale as a strategic investment for a church that is gaining strength, having doubled both its average weekly attendance to 550 and annual congregational support to about $1 million in recent years.

“We know what we need for a sustainable future,” she said. “We want to take this old hymn book, from which we literally sang our praises to God, and convert it . . . into doing God’s ministry in the world today.”

The church’s lay leadership has mostly endorsed the idea — the board of trustees, the finance committee, the church council, and the operating committee all voted in favor, according to Phil Stern, chairman of the board of trustees.

But others remain vociferously opposed, including the church historian and former moderator, Jeff Makholm. A few former lay leaders who guided the church through hard times in the 1980s and 1990s have also spoken out against it.

“Those are obviously longstanding gifts that are important to the church,” said Davis Yetman, whose grandfather began attending Old South shortly after World War I. “I don’t think any previous generation has ever said, ‘We’re so poor we have to sell this.’ And the church has gone through a lot of times harder than this.”

Makholm, an economic consultant from Boston, said the proposal is a hasty, shortsighted, and unnecessary move by clergy and lay leaders who seem indifferent to the division they are sowing in the congregation.

For some of the church’s older members, he added, the psalm book and silver provide a tangible connection to the congregation’s venerable past.

“I think what the government of the church has gotten members into here is a very ugly situation that should have and could have been avoided,” he said.

First formed in 1669, Old South hosted the meetings that led to the Boston Tea Party, baptized Benjamin Franklin on the day he was born, and counted as members Samuel Adams and Phillis Wheatley, heralded as the first published African-American woman poet. Its ornate Northern Italian Gothic building at Dartmouth and Boylston streets in Copley Square, which dates to the late 19th century, is its third home.

The church’s historic assets are on loan to other institutions for safekeeping. The Boston Public Library holds the Bay Psalm Book, and the Museum of Fine Arts keeps the silver.

Even if the sale goes through, Old South will still be rich in historic assets. Its other copy of the Bay Psalm Book, which is in better condition, is part of the Prince Collection — 2,000 or so rare texts collected by the Rev. Thomas Prince, an 18th century pastor of Old South. That collection also resides at the Boston Public Library.

Old South will make its decision in the way congregational churches always have settled debates — by a direct vote of the congregation. A two-thirds majority of the full members in attendance at Sunday’s meeting is required for the proposal to pass. The church has just under 600 full members.

There is no absentee voting, something Makholm says is unfair to the elderly and infirm, and to those who are traveling or who spend some of their time out of state.