Новгородская первая летопись
Ontsifor was first elected posadnik in 1350, when the Novgorod First Chronicle notes that they took the posadnikship away from Fedor Danilovich, whom Ontsifor had accused of murdering his father nine years earlier, and gave it to Ontsifor. Valentin Yanin argues that he was not posadnik of All Novgorod, but was posadnik only of the Nerev End (Konets) north of the Detinets. He and was reelected every year until 1354. The chronicle mentions that in 1354, he voluntarily gave up the office of posadnik. He died in 1367.