2. Based on the phrase, "and you will honor it by not...pursuing your affairs" (Isaiah 58:13), our Sages inferred that concern with one's [weekday] affairs is forbidden [in certain circumstances], even if no "melacha" (one of the 39 categories of forbidden activity) is involved; for example, it is even forbidden to take stock of one's belongings to see what one needs on the following day.
Similarly, it is forbidden to walk through a city to find a horse, boat, or wagon to rent after Shabbos, if it is obvious that one is going for such a purpose (1). One may, however, go out with the intent of guarding one's property or property belonging to a colleague.
(1) If it is not obvious, then the Mishna Berura (306:1) permits it, but the Chaye Odom prohibits it.