וַיִּקְרָ֥א מֹשֶׁ֛ה לְכָל־זִקְנֵ֥י יִשְׂרָאֵ֖ל וַיֹּ֣אמֶר אֲלֵהֶ֑ם מִֽשְׁכ֗וּ וּקְח֨וּ לָכֶ֥ם צֹ֛אן לְמִשְׁפְּחֹתֵיכֶ֖ם וְשַׁחֲט֥וּ הַפָּֽסַח׃

Moses then summoned all the elders of Israel and said to them, “Go, pick out lambs for your families, and slaughter the passover offering. 

וּלְקַחְתֶּ֞ם אֲגֻדַּ֣ת אֵז֗וֹב וּטְבַלְתֶּם֮ בַּדָּ֣ם אֲשֶׁר־בַּסַּף֒ וְהִגַּעְתֶּ֤ם אֶל־הַמַּשְׁקוֹף֙ וְאֶל־שְׁתֵּ֣י הַמְּזוּזֹ֔ת מִן־הַדָּ֖ם אֲשֶׁ֣ר בַּסָּ֑ף וְאַתֶּ֗ם לֹ֥א תֵצְא֛וּ אִ֥ישׁ מִפֶּֽתַח־בֵּית֖וֹ עַד־בֹּֽקֶר׃

Take a bunch of hyssop, dip it in the blood that is in the basin, and apply some of the blood that is in the basin to the lintel and to the two doorposts. None of you shall go outside the door of his house until morning. 

וְעָבַ֣ר יְהוָה֮ לִנְגֹּ֣ף אֶת־מִצְרַיִם֒ וְרָאָ֤ה אֶת־הַדָּם֙ עַל־הַמַּשְׁק֔וֹף וְעַ֖ל שְׁתֵּ֣י הַמְּזוּזֹ֑ת וּפָסַ֤ח יְהוָה֙ עַל־הַפֶּ֔תַח וְלֹ֤א יִתֵּן֙ הַמַּשְׁחִ֔ית לָבֹ֥א אֶל־בָּתֵּיכֶ֖ם לִנְגֹּֽף׃

For when the LORD goes through to smite the Egyptians, He will see the blood on the lintel and the two doorposts, and the LORD will pass over the door and not let the Destroyer enter and smite your home. 

Exodus 12:21-23