827. Writing
Shabbos 23:11
One who smears ointment on Shabbos is liable for performing a subordinate labor of smoothing hides. It is therefore prohibited to seal a hole with wax and similar substances as a preventive measure against smearing. One may not even do so with fat in order to avoid the possibility that one may come to do so with wax.
Shabbos 23:12
Writing is a primary category of Shabbos labor. One is not permitted to apply eye makeup with a brush and similar things on Shabbos because doing so resembles writing. This is also why we may not make financial loans on Shabbos; it is a preventive measure against the possibility of coming to write. It is likewise prohibited to buy, sell or rent out of the concern that one may come to write. One may not hire workers on Shabbos, nor instruct another to do so on his behalf. One may, however, lend and borrow objects on Shabbos, even jugs of wine or oil, provided that he does not make his request in the form of a loan.