In the last Tosfos on 25b (DH Rav), Tosfos quote "HaRav Ezra HaNovi". Do we know anything about this source?
A contemporary of the Or Zaru'a (~1230 CE), Rav Ezra of Moncontour, France, called "Ezra ha'Navi" by his peers, was a pupil of RI Ba'al ha'Tosfos and a mentor of the Maharam of Rotenburg. He is also cited in Tosfos Gitin 88a. (Based on Rav Rafael Halpern's Atlas Etz Chayim, vol. 7:1936).
He is also mentioned in Da'as Zekeinim to Shemos 21:29 (see also Tosfos Rabeinu Peretz to Bava Kama 23b). In fact, he is the "Rav Ezra" that Tosfos mentions, even when he is not called "ha'Navi."
He was a Rosh Beis Din and Rosh Yeshiva in his town, and, according to one Mesores, a decendant of the Ibn Ezra. His appelation was not simply a sign of the high regard in which he was held. Rav Ezra lived during the "Shivas Tziyon" movement in the times of the Rishonim (when Messianic hopes were high), and according to the "Ma'amar Al Shenas ha'Geulah" (an ancient document by Rav Elazar b'rebbi Shlomo, dating from not long after Rav Ezra's passing, printed in "ha'Tzofeh l'Chochmas Yisrael, yr. 5 p. 194), "He went up to heaven and asked the prohets Chagi Zecharyah and Malachi when Mashi'ach would arrive. Each wrote him an answer in three verses..." It was hoped and even expeceted in those days that true prophesy would soon return to our people. (Based on Ba'alei ha'Tosfos by Rav A.A. Auerbach, p. 278.)
He is the author of the commentary on Shir ha'Shirim that is attributed to the Ramban (and printed in Rav Shavel's Kisvei ha'Ramban), and some Kabbalistic treatises (based on Sarei ha'Elef by Rav Menachem Kasher, vol. 1 p. 142 and vol. 2 p. 537).