Mishnah 3 in Maseches Shabbos: A person may not hire workers on Shabbos for work that they will do during the coming week. The Sages forbade speaking on Shabbos about weekday work matters and about melachah that is forbidden on Shabbos, and likewise a person may not tell someone else to hire workers on his behalf for after Shabbos.
The Gemara's precise reading - speech versus thought:
The Gemara explains that the Mishnah chose this wording in order to teach us a fine point: a person may not tell his friend on Shabbos to hire workers for him, but he may say to him, "Meet me tonight, after Shabbos," even though both of them know full well that the purpose is to hire him as a worker once Shabbos is over. The Sages forbade only speaking out loud about work matters, while merely thinking about doing work is not a problem. Therefore, even though both parties know what the meeting is for, as long as it is not said out loud and the purpose is not spelled out explicitly, it is permitted.
Walking to the edge of the techum:
The techum is the boundary beyond which a person may not walk on Shabbos: two thousand amos from the city. The Mishnah rules that one may not wait out the day at the edge of the techum, meaning to walk to its edge and stand there so as to leave the techum the moment Shabbos ends in order to hire workers or to bring produce that will be picked. Both of these activities are forbidden on Shabbos, and therefore one may not walk to the edge of the techum for something that will be done after Shabbos and that cannot be done on Shabbos itself.
By contrast, one may wait out the day at the edge of the techum in order to guard produce after Shabbos, since guarding is permitted even on Shabbos itself. The only obstacle is that he cannot reach the place, because it lies outside the techum; and since the guarding would have been permitted had the place been inside the techum, walking to the edge of the techum for that purpose is permitted.
More than that: once he has arrived there, he may bring produce back with him, even produce that was picked, since the purpose for which he went was guarding and not picking. Bringing the produce is merely incidental to it after the fact.
Abba Shaul's general rule:
Abba Shaul stated a general rule: "Kol she'ani zakai ba'amiraso - rashai ani lehachshich alav" - anything that I am entitled to speak about, I am permitted to wait out the day at the edge of the techum for. In other words, anything that may be spoken about on Shabbos for the sake of doing it after Shabbos may also be the reason for waiting at the edge of the techum. Two categories of things are included in this rule:
Matters bound up with a mitzvah: As will be mentioned in the next Mishnah, there are mitzvah matters that may be discussed on Shabbos for the sake of after Shabbos, even though they involve melachah. And since they may be mentioned on Shabbos, one may also walk to the edge of the techum in order to carry them out.
Matters that are not melachah: Such as guarding produce, which is permitted even on Shabbos itself within the techum. And since they may be spoken about, one may also wait out the day at the edge of the techum for them, as was explained regarding guarding produce that lies outside the techum.
In summary: In this Mishnah we learned that the prohibition against hiring workers on Shabbos stems from the prohibition against speaking about work matters, while thought was not forbidden, and therefore a hint that does not spell out the purpose is permitted. We also learned that one may not wait out the day at the edge of the techum for an activity that is forbidden on Shabbos, but one may do so in order to guard, and may even bring produce back with him. And Abba Shaul summed it all up: "Kol she'ani zakai ba'amiraso - rashai ani lehachshich alav" - anything that I am entitled to speak about, I am permitted to wait out the day at the edge of the techum for.
In the next Mishnah we will deal with matters bound up with a mitzvah, for which both speaking on Shabbos and waiting at the edge of the techum were permitted.