796. The Psak on Plagiarism
The halachic expression for plagiarism is l'hisatef b'itztela she'eino shelo (to wrap oneself in a cloak that is not his), referring to someone who takes a Torah thought, an idea, or the work of another and passes it off as their own. How far must we go in citing the basis of the material we cite? If a secondary source quotes an earlier source, must both authors be referenced?
The Gemara says that when we hear something quoted in the name of someone, who received that information from someone else, who based their conclusion on an even earlier source, we only need to reference the first and last sources, but not the one(s) in between.
There are some poskim who nonetheless say that we are required to cite all sources. Most authorities maintain, however, that our obligation is to quote only the original source, and the stipulation in the Gemara from Chazal to reference the latest source is only minhag tov (a good practice) and not absolutely required.
It may happen that an author thinks of an original concept, and later finds that this idea was presented by earlier sources. The common practice is to write shuv rai'si (I saw it later). However, we are not actually obligated to write shuv ra'isi—it's a matter of common sense and decency, so that others do not assume that the information is plagiarized.
Poskim state that the idea that the expression of shuv ra’isi originated by poskim is a non-obligatory disclaimer for surprise discoveries can be found b’remez (as an allusion) in the Torah: it uses a play on words on the pasuk (verse) in Parashas Vayechi, Bi'rtzonam ikru shor* (“At their whim, they [Shimon and Levi] hamstrung an ox [referring to their brother Yosef]). Utilizing shuv ra'isi—a phrase with the acronym shur—in our creative works is a matter of free will.