zvi yammer asks:
what is the abbreviation at the end of Tosfos מ"ר
zvi yammer, USA
The Kollel replies:
The letters מ"ר stands for מורי רבי (my master my teacher) cited by Tosfos, or מדברי רבי (from the words of my teacher). It refers to the Rabeinu Yitzchak of Dampierre, also known as the Ri ha'Zaken, one of the most prominent of the Ba'alei ha'Tosfos (from the book, Ba'alei ha'Tosfos, by Dr. Efraim Urbach, Mosad Bialik 1955, p. 471).
Avraham Phillips