Shalom Boruch,

I searched and unfortunately could not locate this citation in the Mesivta annotated Tosfos, nor in the editions of Midrash Tehilim available to me. Perhaps someone with access to the Buber edition or other manuscript-based texts can check further -- unless this is in fact a case where the particular Midrash, although the Rishonim had it, has since become lost.

Bi'Vrachah,

Yishai Rasowsky

Shalom Boruch,

I looked into this a bit further and found an interesting discussion.

Buber, in his introduction to Midrash Tehilim , surveys a number of citations in the Rishonim that refer to "Midrash Tehilim." Among them he mentions our Tosfos, as well as several other Rishonim who cite passages that do not appear in any extant edition of Midrash Tehilim . He also notes that another version of this citation refers instead to Midrash Mishlei , but points out that the passage is not found there either.

Buber then suggests that the source may actually be the Zohar (105b), and discusses why the Zohar could have been referred to as a "Midrash," and even as "Midrash Tehilim" in this context. He ultimately rejects this suggestion, however, since it does not appear that the Ba'alei Tosfos were yet familiar with the Zohar.

I would like to suggest another possibility. I found this teaching in Midrash Tanchuma (Bereishis 2), as well as in the She'iltos d'Rav Achai (Bereishis). I have not researched the matter thoroughly, but I wonder whether the original text of Tosfos simply contained the abbreviation Mem-Tav, which was later expanded by a copyist as M'idrash T'ehilim instead of M'idrash T'anchuma!

In any event, the teaching itself does appear in Midrash Tanchuma . See there.

Kol Tuv,

Aharon Steiner