This source comes from a compendium of model shurūṭ, or legal formulae, by Aḥmad b. Mughīth of Toledo (d. 459/1067). In her chapter on imprecatory oaths in Justice and Leadership in Early Islamic Courts, Delfina Serrano uses this source as one of the three foci of her study.
This source is part of the Online Companion to the book Justice and Leadership in Early Islamic Courts, ed. Intisar A. Rabb and Abigail Krasner Balbale (ILSP/HUP 2017)—a collection of sources and other material used in and related to the book.