Hilchot Nedarim

A passage at the end of the Zichronot blessing in the Mussaf Amidah of Rosh Hashanah appears to have two slightly different versions. The Shulchan Aruch (Orach Chayim, 591:7) rules that this is the correct text: “V’akeidas Yitzchak hayom l’zaro tizkor.” It also rules and those who change the words and specify “l’zera Yaakov tizkor” are mistaken and guilty of changing the text instituted by Chazal. The source for this ruling is a responsum (chapter 38) by the Spanish and then Algerian Rivash (14th century).