Rabbi Shmuel Strashun, known as the Rashash, was born in Zaskevich, in the Vilna region, on 18 Cheshvan 5554 according to the Hebrew Wikipedia (other sources give 1794). The son of Rav Yosef Shmuelson, he studied with his father and with Rabbi Avraham Danzig; the English Wikipedia also mentions study under Rabbi Shemariah Rabinowitz in Kreva.

He married Sarah, daughter of the wealthy Rav David of the village of Strashun, whose name he adopted. In 1812, during Napoleon's invasion, he moved with his father-in-law to Vilna, where the latter founded a study hall. With her inheritance, Sarah established a successful distillery business that allowed her husband to devote himself to learning; he also served as chief proofreader at the Romm printing house.

He held no rabbinic office and turned down a rabbinic post in Suwalki. He was active in the communal affairs of Vilna, ran a large free-loan fund, and every morning gave a two-hour Talmud class to a select group of young men and avreichim.

His glosses and novellae on the entire Babylonian Talmud, born of these classes, are printed at the end of the volumes of the Vilna Shas (Romm edition) and became a standard commentary in the yeshivot. He also annotated the Midrash Rabbah, the Rambam's Mishneh Torah, the Vilna Gaon's Maaseh Rav and the Shulchan Aruch. His son Matityahu Strashun founded the famous Strashun Library.

He passed away in Vilna on 11 Adar II 5632 (21 March 1872). The community's rabbinical court declared a general cessation of work for his funeral, and he was buried in the Jewish cemetery of Vilna, beside Rabbi Avraham Abele Posvoler.