The call came out of the blue. Would the N.C. Museum of Art be interested a painting by John Singer Sargent?

John Coffey, the museum's curator of American and modern art, was skeptical. The likelihood that a person owned an original Sargent, considered the leading portrait painter of the late 19th and early 20th century, is small. The likelihood that person would want to donate such a treasure, even smaller.

The donor, who asked to remain anonymous, said he was impressed with the museum's renowned Judaic art collection. Though he is not Jewish, he thought his painting would complement it.

It didn't take long after Coffey saw the painting to realize it was, in his words, "a keeper."

The oil sketch titled "Israel and the Law" is part of Sargent's monumental mural cycle "The Triumph of Religion" at the Boston Public Library. The painting depicts a hooded God shielding a boy counting on his fingers, memorizing the commandments from a scroll in God's hands. Six angels flank the two, their swords drawn.

"They're very lucky to have this painting," said Sarah Schroth, curator of the Nasher Museum of Art at Duke University. "Sargent is one of our top American artists. Having a Sargent in any form is a bonus for a collection."

Though he is celebrated as a portrait painter of Boston's wealthy aristocrats, Sargent also undertook mural projects for public institutions, such as Boston's library and museum.

The library project, Sargent's most ambitious, depicts in several panels the evolution of religion from polytheism to the divine revelations of Judaism and Christianity. Sargent worked on the project from 1890 to 1919 and did numerous sketches of the various murals in pencil, charcoal, oil and clay.

"Israel and the Law" was one of Sargent's most challenging panels, designed for a wall surface in the shape of a half moon. He prepared by painting two smaller oil sketches of what he planned to do on a larger scale. One hangs at the Royal Academy of Arts in London. The other is now in Raleigh.

"Aside from it being by a major American artist, it's the first civic painting we have in the American collection," Coffey said. "It helps us expand the story of American art. Paintings are not just intended to go in houses but were intended also to decorate public buildings and educate the public."

Though not religious, Sargent was ambitious. He recognized that religion was one of the grand themes of human history and that taking it on would solidify his credentials.

"Any academically trained artist wants to be known for their ability to interpret history, and a religious painting is a historical painting," said Schroth, the Nasher curator.

To properly display the painting, which measures 37 inches by 59 inches, Coffey had a special frame built to re-create the Boston Public Library setting. He asked for swatches of the wall's color - a gray limestone - and commissioned a local furniture maker to build a frame that would give context to the grandeur of the Italian-style building.

"Changing out the frame gives a meaning to the painting," Coffey said.

Last week, the painting went up outside the Judaic gallery, alongside some explanatory comments on the library murals and Sargent's work. The painting will remain in the same spot for about a year, Coffey said. Later, it might be integrated into other galleries in the museum.

"It's an important work by a major American artist," Coffey said. "I'm just giddy we have it."

Yonat Shimron is a former reporter for The News & Observer.