Sobor of 1503, also known as the "sobor of widowed priests" was a sobor of the Russian Orthodox Church, which was held in Moscow between August and September 1503. The sobor was convened at the initiative of Simon, Metropolitan of Moscow. The main task of the sobor was to resolve a number of disciplinary matters in respect of which it issued two rulings. However the Sobor is primarily remembered as dealing with the controversy of the 'nestyazhateli' or non-possessors. The non-possessors, lead by Nilus of Sora opposed monastic landownership. They were faced by the possessors (styazhateli), led by Joseph of Volotsk, who asserted that monasteries needed lands to finance their activities. The debate between the possessors and non-possessors would continue until the Stoglav Sobor in 1551.