According to Exodus 12, lamb’s blood was placed on the doorposts and what top beam of Israelite homes? It was placed on the lintel, the horizontal beam above a doorway. Exodus 12 describes the Israelites marking their doorposts and lintels with the blood of the Passover lamb.
In the biblical narrative, this sign distinguished Israelite homes during the final plague in Egypt. The Israelites were instructed to slaughter a lamb, apply its blood to the entrance, and eat the meal that night. The passing over of those marked houses gives the festival its name and establishes the ritual’s commemorative meaning.
A lintel is not the threshold, which is the sill or floor-level part of a doorway, and it is not a rafter, which supports a roof. The instruction concerns the doorway’s upright posts and its top beam. Later Passover practice changed when sacrifice became centered at the sanctuary and, eventually, the Jerusalem Temple rather than private homes.