תלמוד על נדרים 11:7

Rebbi Eleazar ben Arakh says, “bespeaking” acquires a sister-in-law completely. What is the argument of Rebbi Eleazar ben Arakh? “And take her as wife for himself”, the same expression is used as for qiddushin of a woman¹⁹Deut.22:13, “If a man takes a wife”.. Just as qiddushin acquire completely, so “bespeaking” acquires a sister-in-law completely. What is the formula for “bespeaking” a sister-in-law? “You are betrothed to me by money or money’s worth.²⁰The same formula as for qiddushin; Babli 52a, Tosephta 1:1 (the latter also has the formula for “bespeaking” by document).”