Bava Basra, Chapter 5, Mishnah 3 (page 53b). The Mishnah continues to discuss what is included in the sale of various items when the details are not specified in the conditions of the sale.
Selling a Donkey and Selling a Cow:
"Hamocher es hachamor - machar es hasayach" - One who sells a donkey has sold the foal. The Gemara explains that this is not referring to a standard donkey, but to someone who announces that he is selling a nursing donkey. Seemingly, mentioning the nursing is meant to point out a virtue and advantage, but since that which emerges from an impure animal is not kosher, the milk is of no use to anyone. Rather, the nursing teaches that a foal accompanies it, and therefore the foal - the offspring of the donkey - is included in the sale and comes along with it.
"Machar es haparah - lo machar es benah" - If he sold a cow, he has not sold its offspring. When a person sells a cow and notes that it is nursing, the nursing itself is the great advantage: a nursing cow is a cow with abundant milk, and cow's milk is kosher, which is what the buyer seeks. Because of this, the offspring, the calf, is not included in the sale.
Four Places Whose Contents Are Included in the Sale:
The Mishnah lists four physical places on top of which or inside of which movable items are placed, and in all of them the contents are sold together with the place:
"Machar ashpah - machar zivlah" - One who sells a dung heap has sold its manure. When someone sells the place designated for storing manure (an area raised above the ground or dug into it by a measure of three handbreadths or more), all the manure and fertilizer found there at that time are included in the sale.
"Machar bor - machar meimav" - One who sells a cistern has sold its water. When someone sells his water cistern, the water inside it transfers with it.
"Machar kaveres - machar devorim" - One who sells a beehive has sold the bees. When someone sells a beehive, the bees inside it transfer with it.
"Machar shovach - machar yonim" - One who sells a dovecote has sold the doves. When someone sells a dovecote, the place where he raises doves, the birds transfer together with the sale.
The Gemara notes that this is the opinion of Rabbi Nasan, and the Sages disagree with him at least in the case of the cistern. According to their view, the water is not sold with the cistern, because water - unlike manure, doves, and bees - is necessary for every person every day, and therefore it is a different type of item: the seller does not agree to sell his water, but rather seeks to keep it for himself. The question of whether the halachah follows Rabbi Nasan or the Sages is a dispute reflected in the Shulchan Aruch and the Rema.
Purchasing Future Output:
From here the Mishnah moves to a case where a person sells his friend the output of a "factory" (figuratively speaking) that produces fledglings or bees, and the buyer wishes to purchase the entire yield. Since the owner of the "factory" intends to continue producing in the coming years as well, it is clear that he does not intend to hand over everything: if he were to hand over all the birds or all the bees, he would have nothing left for the next year. The question is, therefore, what exactly is included in the transaction.
"Haloke'ach peiros shovach meichaveiro - mafriach bereichah rishonah" - One who buys the produce of a dovecote from his friend must let the first brood fly. A person who agreed with his friend to purchase the entire output of the dovecote, meaning all the birds that will hatch during the year, does not receive the first group of fledglings that hatched.
To understand the matter: Doves and turtledoves lay a pair of eggs, a male and a female, every month, and the parents remain in the dovecote as long as the first pair is found there, in order to care for it and invest in it. This pair is called a "brood," and the Mishnah rules that one must leave the first brood - the two offspring of the parents - so that the parents do not leave the dovecote. The rest of the birds that hatch during the year are given to the buyer. In the normal course of events, two additional eggs are laid each month which become fledglings, and when these mature after a few months they themselves begin to lay. The Gemara adds that one must leave not only the first generation of offspring, but even the first generation of "grandchildren," so that all the birds will remain in their place; the "grandchildren" born afterward transfer to the buyer as well. It turns out that the buyer receives all the "children and grandchildren" of the birds, aside from the first brood, and this is so that the bird-raising business does not come to an end.
It is proper to be precise with the wording: "Mafriach" is a causative term - to make them fly away and send them back. This should not be understood literally, but rather that the buyer is not entitled to receive them in the first place: the first cycle of fledglings that hatch to the parents is not included in the sale at all.
The produce of a beehive:
The next case is a person who agrees with his friend to receive the entire output of a beehive, meaning all the bees that emerge from it as a swarm during that year. The nature of beehives is that during the summer season, a new swarm emerges from them approximately every ten days, resulting in a total of about seven or eight groups. Here too, it is clear that the seller did not intend to hand over all of them, for if he did, he would not have a functioning beehive left for the following year, and therefore he is entitled to keep a portion of them for himself.
"Notel sheloshah nechalim u'mesares" - the first three swarms that emerge in the summer are the most important and primary ones, and they go to the buyer. From then on, they alternate: the fourth swarm stays with the original owner, the fifth goes to the buyer, the sixth stays with the owner, the seventh goes to the buyer, and so on.
Honeycombs:
Bees build honeycombs in order to store, among other things, honey. A person who wants the honey takes the honeycomb, empties it, and returns it to its place. However, if he were to take all the combs, the bees would not be able to survive the winter, and therefore the Mishnah addresses how much is included in the sale and how much must be left behind. "Chalos devash - maniach shetei chalos" - one must leave two honeycombs so that the bees can survive the winter, and the rest of the combs go to the buyer.
Why is bee honey kosher, when at the beginning of the Mishnah we stated that what emerges from an impure animal - such as donkey milk - is not kosher? The Gemara provides two reasons:
The bee does not produce the honey as a bodily product or excretion. Rather, the nectar that it ingests turns into honey in its stomach and it regurgitates it, meaning it is not something actually generated from its body.
The Gemara in Tractate Bechoros states that this is a scriptural decree, and there is a derivation for this from a verse.
Olive trees for chopping:
The final case deals with someone who sells the branches of his olive tree for wood: the buyer wants firewood, and the owner of the tree agrees to sell him its branches. Here too, the seller does not want to sell all the branches, for if he does, the tree will die and will no longer produce olives. "Zeisim lakotz - maniach shtei gerufiyos" - he must leave two branches that will sprout more olives, and the rest are sold.
This Mishnah, like all the Mishnayos of this chapter and the previous one, is based on the meaning that an average person would expect, and how the Mishnah understood the intent of a buyer and seller in the Land of Israel during the second and third centuries CE, the time and place in which it was written. In any other time and place, where people speak, relate to things, and have different expectations, the halachah will change accordingly.