Question: Who won the commission from the Operai?
About the article "David (Michelangelo)", section "Commission".

Candidate passages:
The history of the statue begins before Michelangelo's work on it from 1501 to 1504.
Prior to Michelangelo's involvement, the Overseers of the Office of Works of Florence Cathedral, consisting mostly of members of the influential woolen cloth guild, the Arte della Lana, had plans to commission a series of twelve large Old Testament sculptures for the buttresses of the cathedral of Santa Maria Del Fiore.
In 1410 Donatello made the first of the statues, a figure of Joshua in terracotta.
A figure of Hercules, also in terracotta, was commissioned from the Florentine sculptor Agostino di Duccio in 1463 and was made perhaps under Donatello's direction.
Eager to continue their project, in 1464, the "Operai" contracted Agostino to create a sculpture of David.
A block of marble was provided, from a quarry in Carrara, a town in the Apuan Alps in northern Tuscany.
Agostino only got as far as beginning to shape the legs, feet and the torso, roughing out some drapery and probably gouging a hole between the legs.
His association with the project ceased, for reasons unknown, with the death of Donatello in 1466, and ten years later Antonio Rossellino was commissioned to take up where Agostino had left off.
Rossellino's contract was terminated soon thereafter, and the block of marble remained neglected for twenty-five years, all the while exposed to the elements in the yard of the cathedral workshop.
This was of great concern to the "Opera" authorities, as such a large piece of marble not only was costly but also represented a large amount of labour and difficulty in its transportation to Florence.
In 1500, an inventory of the cathedral workshops described the piece as "a certain figure of marble called David, badly blocked out and supine."
A year later, documents showed that the "Operai" were determined to find an artist who could take this large piece of marble and turn it into a finished work of art.
They ordered the block of stone, which they called "The Giant", "raised on its feet" so that a master experienced in this kind of work might examine it and express an opinion.
Though Leonardo da Vinci and others were consulted, it was Michelangelo, only twenty-six years old, who convinced the "Operai" that he deserved the commission.
On 16 August 1501, Michelangelo was given the official contract to undertake this challenging new task.
He began carving the statue early in the morning on 13 September, a month after he was awarded the contract.
He would work on the massive statue for more than two years.
He had no formal education after grade seven, when he was expelled, but read widely in philosophy and art.
At an early point he became interested in avant-garde art and experimentalism.
He also became close to leftist intellectuals and artists His first novel, "Tre Operai" ("Three Workers"), concerned workers issues in Naples.
The book may have been a precursor to neo-realism and reportedly angered Benito Mussolini who felt there was Communism in it. 
In 1873 the statue of David was removed from the piazza, to protect it from damage, and displayed in the Accademia Gallery, Florence, where it attracts many visitors.
A replica was placed in the Piazza della Signoria in 1910.
In 1991, a man attacked the statue with a hammer he had concealed beneath his jacket, in the process damaging the toes of the left foot, before being restrained.
On 12 November 2010, a fiberglass replica of the "David" was installed on the roofline of Florence Cathedral, for one day only.
Photographs of the installation reveal the statue the way the "Operai" who commissioned the work originally expected it to be seen.
In 2010, a dispute over the ownership of David arose when, based on a legal review of historical documents, the Italian Culture Ministry claimed ownership of the statue in opposition to the city of Florence, where it has always been located.
Florence disputes the state claim. 
After Cosimo's triumphant return to Florence, rather than scrapping the project, in May 1436 the Medici regime hired Uccello to replace the Gaddi and Pesello fresco.
Hugh Hudson suggests that it would have been too risky for the Medici to cancel the Albizzi project, so they instead shrewdly modified it to fit their interests.
There is, of course, some weakness to attributing the commissioning and re-commissioning of the monument to Albizzi or Medici intrigues, as only two (maybe three) of the eight "operai" on July 13, 1433 were members of the Albizzi faction and only one was a Medici when it was resumed on May 18, 1436; yet the influences of both factions doubtlessly did not require blood relation.
Around this time, documents attest to multiple repairs of a nearby window, opening the possibility that the original fresco had experienced water damage, and would have needed to be restored in any case.
Others have suggested that the recommissioning was part of the "refurbishing" of the cathedral associated with its rededication as Santa Maria del Fiore by Pope Eugene IV in March 1436.
Yet, Borsi concludes that "undoubtedly under pressure from the Medici" the "operai" discarded their plans for a straightforward restoration of the Gaddi fresco and opted for a completely new monument. 
Donatello was commissioned to carve a statue of David in 1408.
The commission came from the "operai" of the cathedral of Florence, who intended to decorate the buttresses of the tribunes of the cathedral with 12 statues of prophets.
Nanni di Banco was commissioned to carve a marble statue of Isaiah, at the same scale, in the same year.
One of the statues was lifted into place in 1409, but was found to be too small to be easily visible from the ground and was taken down; both statues then languished in the workshop of the "opera" for several years.
In 1416 the Signoria of Florence commanded that the "David" be sent to their palazzo; evidently the young David was seen as an effective political symbol, as well as a religious hero.
Donatello was asked to make some adjustments to the statue (perhaps to make him look less like a prophet), and a pedestal with an inscription was made for it: PRO PATRIA FORTITER DIMICANTIBUS ETIAM ADVERSUS TERRIBILISSIMOS HOSTES DII PRAESTANT AUXILIUM (To those who fight bravely for the fatherland the gods lend aid even against the most terrible foes).
The marble "David" is Donatello's earliest known important commission, and it is a work closely tied to tradition, giving few signs of the innovative approach to representation that the artist would develop as he matured.
Although the positioning of the legs hints at a classical contrapposto, the figure stands in an elegant Gothic sway that surely derives from Lorenzo Ghiberti.
The face is curiously blank (curiously, that is, if one expects naturalism, but very typical of the Gothic style), and David seems almost unaware of the head of his vanquished foe that rests between his feet.
Some scholars have seen an element of personality – a kind of cockiness -(contrapposto=relaxed stance, shifted weight) suggested by the twist of the torso and the akimbo placement of the left arm, but overall the effect of the figure is rather bland.