Making Waves On Shabbos
The Gemara in Shabbos makes an undisputed statement: Less than three days before Shabbos, one is not allowed to board a boat that will travel on Shabbos unless the travel is for the purpose of a mitzvah.
Medicine and Health
Scheduling Surgery Before Shabbos in the Gemara
Planning non-emergency surgery or a tooth extraction early in the week so that recovery will not require breaking Shabbos or spoil its enjoyment.