You wrote

>>"(RAV DOV BIDERMAN, in his commentary to the Toras Kohanim, writes that it was revealed to him in a dream that this is why Rabeinu Yakov ben Meir, the grandson of Rashi, was destined to be known as "Rabeinu Tam." After he instituted the enactment that the Nedunya returns to the father if the daughter dies within the first year, the curse of "v'Tam la'Rik Kochachem" no longer applied, according to the Toras Kohanim's interpretation of that curse. If the Kalah died during Sheva Berachos, the money would go back to the father and he would not lose his money! Since Rabeinu Yakov's enactment voided the curse of "v'*Tam* la'Rik Kochachem," he was called "Rabeinu Tam.")<<

Where can I find this Sefer?

Avrohom Sebrow