The Twelve Tribes lithographs after Chagall based on preliminary sketches for the Jerusalem stained-glass windows. In 1959 Chagall was commissioned to design twelve stained glass windows for the new synagogue of the Hadassah-Hebrew University Medical Centre, situated in the Judean hills west of Jerusalem. The number twelve is considered spiritual and sacred. These magnificent windows symbolise the twelve sons of Jacob from whom sprang the twelve tribes of Israel. Keen that his designs be more widely disseminated, Chagall was closely involved with the production of the set of lithographs based upon his studies, created by the world famous Mourlot Frères of Paris: the publisher, James Parton, recalled how the artist stood beside the lithographer to watch the single sheets pass through the hand-fed stone press, one colour at a time...to catch every nuance of shading. [He] threw out the whole first set of gravure plates: the yellow, he felt, was off a shade.