Gittin, Chapter 6, Mishnah 5. This Mishnah distinguishes between the various expressions a husband may use when instructing his agents: there are expressions that clearly indicate his wish that they write and deliver a get to his wife, and there are expressions that do not necessarily indicate this, and can therefore be understood as referring to something other than a get.
Expressions that indicate a get:
"Kisvu get u-tnu l'ishti" - his intention is explicit: they should write a get and give it to his wife.
"Garshuha" - he used the language of divorce, which means actual divorce: divorce her on my behalf.
"Kisvu iggeres u-tnu lah" - the literal meaning of 'iggeres' is a letter, but the get itself is called "iggeres shevukin" within the body of the document. It emerges that 'iggeres' is one of the terms by which a get is described.
In all of these cases the halachah is "harei eilu yichtevu v'yitnu" - the witnesses to whom this was said write the get and give it to her.
Expressions that do not indicate a get:
"Pitruha" - a term of exemption and relief, which can be understood as releasing her from her monetary obligations.
"Parnesuha" - a term of support, and it is possible that he does not intend to divorce her at all, but rather to provide for her and her financial needs.
"Asu lah k'nimus" / "Asu lah kara'uy" - do for her what is fitting and appropriate, and this too may be understood as providing for her food and clothing.
In each of these cases the halachah is "lo amru klum" - these statements carry no legal consequence whatsoever regarding divorce.
"Hayotzei b'kolar":
At first they would say: one who goes out in a kolar - a person being led out in chains, who is presumably about to be executed by the government - who said to two people, "Kisvu get l'ishti", they should write the get and give it.
Ordinarily, when a person says "write a get for my wife," he must also add "and give it," that is, he must instruct his agents not only regarding the writing but also regarding the delivery. In this case, however, since he is about to die, he is not in a frame of mind in which he can be precise in the wording of his instructions. Therefore his very instruction to write the get testifies that he wants it delivered as well, and even though he did not say "give it" - they write it and give it.
Broadening the halachah:
Afterward the Sages did not change this halachah but added to it, ruling that not only in this case, but in all of the following as well:
One who sets out on a long sea voyage.
One who sets out with a caravan into the desert.
The dangerously ill - one whose life is at risk on account of a serious illness.
All of these are situations of great danger, and the person does not know whether he will return. Therefore in these cases too, if he said "write a get for my wife" and did not say "give it," the witnesses may write the get and even deliver it to her.
In summary: In this Mishnah we learned the distinction between expressions that indicate a get - "Kisvu get u-tnu l'ishti," "Garshuha," "Kisvu iggeres u-tnu lah," in which case "harei eilu yichtevu v'yitnu" - and expressions that do not indicate a get - "Pitruha," "Parnesuha," "Asu lah k'nimus," "Asu lah kara'uy," in which case "lo amru klum." We also examined the enactment of the Sages regarding one who goes out in a kolar, which was extended to one who sets out to sea, one who travels with a caravan, and the dangerously ill, in all of whom the word "write" alone suffices, even without "give."