Mystery surrounds the exhilarating new exhibition at the Frick Collection, “Jacob and His Twelve Sons: Paintings from Auckland Castle,” by the Spanish artist Francisco de Zurbarán (1598-1664).

The series of 13 paintings, each one looming more than six feet tall, makes for a majestic gallery of vibrantly detailed portraits. With each canvas devoted to just one massive solo figure, the effect of taking them in one after another is of a holy procession. Seen as a whole, the impression is that of a sacred gathering where each individual is distinctively garbed to personify a particular biblical character’s personality or temperament.

Here is Jacob the patriarch, squinting beneath an elaborately tied turban and bent nearly in half, seemingly from the weight of his waist-length beard. Judah is posed, as befitting the ancestor of the Kings David and Solomon, in regal robes, with a scepter and crown and a lion crouching beside him. Benjamin, the youngest, wears a youthfully fanciful outfit that features a striped vest and decoratively laced bows, and in addition sports a shoulder bag that alludes to the story of the silver cup that his brother Joseph (who is portrayed in another canvas, cloaked in stately fur and bearing a high official’s rod and petition) had hidden in his sack of grain.

Each of the other figures is just as striking in his own way, the costumes as exotic as they are evocative, their stature lending them a compelling presence.

“Courtesy of The Frick”

But the very reason for these paintings’ existence is an enigma.

Unanswered questions abound: Why, after the expulsion of the Jews from Spain, at a time when even the hint of Jewish religious practice still risked persecution by the Inquisition, would an artist famed for his depictions of Christian saints and pious monks turn to the entirely uncharacteristic subject for him of figures from the Hebrew Bible? Why take such exquisite care to suggest in the very stance, bearing and clothing of each figure the verses from Genesis (49:1-20) in which the aged patriarch Jacob gathers his 12 sons around him to bless and prophecy their future as the founders of the tribes of Israel?

There’s even the quality of a whodunit as to how and why all 13 paintings disappeared from sight shortly after their completion in the 1640s, only to reappear without explanation some 80 years later at a European auction house where they were bought by James Mendez, a Portuguese Jewish merchant and collector. But perhaps the most unusual twist of all is where the paintings ultimately landed after Mendez’s death: on the dining room walls of the imposing thousand-year-old Auckland Castle in Durham, England. They were hung there in 1756 by the Anglican Bishop Richard Trevor as an unmistakable statement in favor of equal rights for Britain’s Jews, at a time when they could not vote or hold office. And that is the home to which the paintings will return after the conclusion of this exhibition.

“This is a fantastic set of paintings that is wrapped in stories and myths and conjectures,” says Susan Grace Galassi, senior curator at the Frick collection and coordinating curator for the exhibition. What is clear is the technical mastery visible in the choice of striking color combinations, the rendering of the textures, patterns, and folds of the figures’ elaborate costumes, and in the humanity and individuality of the faces of each of the sons.

As for the question of how they came to be, the most likely explanation, says Galassi, is that they were originally destined for export to the Spanish colonies of Latin America. Bolstering that theory is the fact that that at least two other sets, connected with the Auckland Castle series, are known in churches in Lima, Peru, and Puebla, Mexico. Many people in 16th- and 17th-century Spain believed that the indigenous peoples of the Americans were the descendants of the so-called “ten lost tribes of Israel.” These are the tribes that fled the kingdom of Israel in the eighth century BC, after the Assyrian conquest, supposedly settling in distant, unknown lands. Following that theory, in the New World, “Jacob and His Twelve Sons” could be viewed as the remote ancestors of the native people whom missionaries were converting to Christianity.

“Courtesy of The Frick”

Although there is no record for any commission for the series, Galassi suggests another possible clue that points to the set’s intended destination in the New World: the multicolored striped, cropped pants worn by Zebulun, which evoke textile patterns from the Americas. This son is portrayed as a sailor, holding an anchor in one hand, and a barge pole in the other.

Zurbarán appears to have paid close attention to the descriptions of the sons in Jacob’s farewell speech in Genesis, but there are allusions to other biblical passages as well. For example, in the verses from Genesis Jacob rebukes both Simeon and Levi for their brutal slaughter of the men of Shalem as punishment for Shechem’s rape of their sister Dinah. Reflecting this savagery, Simeon is clothed in animal skins from head to toe, with the exception of a blood red sash. Holding a sword and cudgel, he strides through a desolate landscape. Not so for Levi, who is depicted as a high priest — a reference to Deuteronomy 18: 107, where Moses explains that God has chosen the Levites to serve as priests.

Does Galassi herself have a favorite? “I love the aggregate, the variety,” she says. But what captures her imagination in particular is the way that Zurbarán has modeled Jacob’s eyes so that they appear to be looking out at us as he speaks the words in Genesis, “Gather around, that I may tell you what will happen to you in days to come. Assemble and hear, O sons of Jacob; listen to Israel your father.” With his artistry, Zurbaran also draws us in. “It’s as if we’re partaking of the gathering and are in a way part of that circle, too, and receiving a blessing as well.”  n

“Jacob and His Twelve Sons: Paintings from Auckland Castle” runs through April 22 at the Frick Collection, 1 E. 70th St., frick.org.