Rav Yitzchak Isaac Krasilschikov was born in 1888 in Kritchev, in White Russia (today Belarus), to Rav Dov Ber. He studied at the Mir Yeshiva when it was headed by Rav Eliyahu Baruch Kamai.

Before the Communist revolution he served as rabbi of Haditch and then of Poltava, which earned him the title "Gaon of Poltava." There, in 1926, he printed the first part of Tevunah, his novellae on the Rambam's Mishneh Torah, considered the last Torah work published in Communist Russia.

As the persecution of rabbis intensified, he left the rabbinate and from 1929 lived in Moscow, working as an accountant by day and studying Torah at night. During the Second World War he moved to Krasnoyarsk in Siberia, returning to Moscow after the war.

In secret, and with almost no reference books, he wrote a dual commentary on the Jerusalem Talmud (the orders of Zeraim and Moed): Toldos Yitzchak, a clear running explanation, and Tevunah, deeper discussions and textual emendations, together some twenty large manuscript volumes.

From his hospital bed in Moscow, the day before his death, he revealed the existence of the manuscripts to Rav Tzvi Bronstein of the United States, who after many attempts succeeded in smuggling them out of the Soviet Union. They were published from 1980 by the Mutzal Me'esh Institute with the approbations of leading Torah authorities. The second part of Tevunah on the Rambam, rescued the same way, appeared in 1976 through Mossad HaRav Kook. Rav Krasilschikov passed away in Moscow in Iyar 5725 (May 1965).