Rabbi Shabsai ben Meir HaKohen, known as the Shach after his principal work, was born in 5382 (1621 or 1622) in Amstibova, in the Polish-Lithuanian Commonwealth; some sources give Vilna as his birthplace. His father, Rabbi Meir HaKohen, a student of the Maharam of Lublin, served as rabbi of Amstibova.

As a child he studied with Rabbi Natan Nata Shapira, author of Megaleh Amukot, and at the age of twelve entered the yeshiva of Rabbi Yehoshua Heshel of Krakow, author of Magen Shlomo. He continued his studies in Lublin. In 5411 (1651) he was appointed a member of the Vilna rabbinical court.

At twenty-four, in 1646, he published in Krakow his commentary on Shulchan Aruch Yoreh De'ah, Siftei Kohen (the Shach), later followed by his commentary on Choshen Mishpat. His writings drew the hostility of some contemporaries, among them Rabbi David HaLevi, author of the Turei Zahav (the Taz), whose work he criticized in Nekudot HaKesef.

Works: Siftei Kohen on Yoreh De'ah and Choshen Mishpat, Sefer HaArokh on Tur Yoreh De'ah, Tokfo Kohen, Poel Tzedek, Gevurat Anashim, Nekudot HaKesef, and Megillat Eifah (Amsterdam, 1651), a lament and selichot on the massacres of 1648-1649.

During the conquest of Vilna in 1655 he fled with the entire Jewish community and wandered from place to place until he reached Holešov in Moravia, where he was received as rabbi. He passed away shortly afterwards, on 1 Adar, at about forty-one, and was buried in the Jewish cemetery of Holešov. Sources differ on the year: 1 Adar 5422 (20 February 1662) or 1 Adar I 5423 (8 February 1663).