Leil Shimurim (Seder Night — Night of Divine Protection)

The practice of treating the Passover Seder night as divinely protected (leil shimurim, "night of watching"), expressed through the omission of additional protective prayers normally recited at bedtime (only Shema and Birkat HaMappil are said) and the custom of leaving the door unlocked or open during Shefokh Chamatekha. Grounded in the Talmudic ruling that the four cups need not be avoided despite the usual concern about pairs (zugot), because the night is "guarded from harm" (Pesachim 109b), and in Rema's gloss citing the Or Zarua's practice of not bolting doors as a public act of faith in divine protection. Codified for all Ashkenazim via Rema (Shulchan Aruch OC 481, 16th-c. Krakow); adopted across Sephardic practice through Kitzur Shulchan Arukh and Arukh HaShulchan. The open-door gesture during Shefokh Chamatekha became near-universal. Extended nighttime Seder celebration (prolonging into the small hours) is attested as early as the Haggadah narrative of the five Tannaim at Bnei Brak, and was emphasized in Chasidic communities from the 18th century; the specific claim that the Baal Shem Tov institutionalized a Seder-to-dawn vigil lacks a sourced first attestation and should not be stated as fact.