A tiny book of psalms from 1640 owned by Boston's Old South Church could bring as much as $30 million when it goes on the auction block tonight at Sotheby's in New York.

Nancy Taylor, senior minister and CEO of the church, says it wasn’t an easy decision.

“In the end, Old South Church of Boston is not a library or a museum," Taylor said. "We’re a church. And we’re in the extraordinary position of having two Bay Psalm books, and we have decided after a very long and thoughtful process to convert one into fuel for our mission and our ministries.”

Old South Church is open to the public daily, and the Taylor says the money from the sale will help maintain the building in addition to financing their charity causes.

“We work with people with HIV/AIDS, we work on youth violence in the city, we work with homeless people and housing. We’re excited to be able to focus more on those with the help of this book.”

The sale of the Bay Psalm Book could set an auction record for any printed book.

A copy of John James Audubon's "Birds of America" is the current record-holder. It sold for $11.5 million at Sotheby's in 2010.