Yahrtzeit of Rabbi Yoel Sirkes (1561-1641), known as the "Bach," an acronym of his famous work of Jewish law, Bayit Chadash. Rabbi Sirkes served in several rabbinic posts throughout Poland, lastly as Chief Rabbi of Krakow. He was the teacher and father-in-law of Rabbi Dovid HaLevy, who authored the famous work of Jewish law, Taz (Turei Zahav).
Adar 20 is also the yahrtzeit of Rabbi Shlomo Zalman Auerbach (1910-1995), leader of Jerusalem Jewry for much of the 20th century. Rabbi Auerbach possessed a phenomenal command of talmudic literature, and he answered tens of thousands of questions posed from all corners of the world. His rulings -- most notably on scientific, technological and medical matters -- have been published in numerous volumes. Rabbi Auerbach was beloved for his piety and concern for every Jew; he was known to delay prayer services until the street-sweeper arrived. Incredibly, Rabbi Auerbach testified that throughout his entire marriage, he and his wife never once offended or hurt one another. Rabbi Auerbach was so beloved that an estimated 300,000 people attended his funeral -- the largest funeral in Israel since Mishnaic times.