Leviticus 26:42

This verse is recited as part of the prayer that follows the morning recitation of the akeidah. Rashi points out that this is one of five places where the name “Yaakov” (Jacob) is written “malei,” i.e., with the letter vav. (It usually has just the dot needed to make the “O” sound but not the vav under the dot.) There are also five places where the name “Eliyahu” (Elijah) is written “chaseir,” i.e., without the letter vav that it normally has. Metaphorically, Rashi tells us, Yaakov took the vav as collateral to ensure that Eliyahu will come to announce the redemption of Yaakov’s children, the Jewish people.