In a situation where two people argue over the ownership of an object – one claims that he rented it or lent it to the other, and the second one says that he bought it – several different issues must be considered. For example, is this an object that is ordinarily rented or lent? Even terms like these need to be defined. While the Rambam understands that an object that is rented or lent refers only to things that are made specifically for that purpose, e.g. a very large pot that is not used for ordinary cooking, but would only be used when preparing for an out-of-the-ordinary meal. Such a pot would be purchased by someone specifically with the intent that it would be available to others for occasional use. Most rishonim, however, understand that concept more broadly and any item that is commonly lent to others would fall into that category.
A specific example of something that is lent or rented is mentioned by the Gemara as something that Rava once collected from orphans – from the children of someone who had borrowed them from another. In that case he made them return a pair of scissors and books of aggadic teaching, both of which are identified as things that are commonly lent or rented.
Rashi understands that the books of aggadic teachings are the only books that we anticipate that someone would lend out, since they are used only occasionally. Books on topics of halakha, however, which are referred to on a regular basis, we assume would not be lent to others, since they would become worn with use. Tosafot reject Rashi’s interpretation and argue that books of aggadic teachings are mentioned because we may have thought that they were not lent to others since they are studied only occasionally. Other books that are commonly referred to are certainly lent out. The Ri”d distinguishes between a Sefer Torah that is not readily lent to others, since there is concern with the erasure of even a single letter; other books, however, are commonly lent without concern.