Question: Why is this necessary?

It is not needed to acquire them. He can acquire through Chalipin!

Suggestion: It is to permit them on Yom Tov (so they will not be Muktzah).

Rejection: It suffices to say (before Yom Tov) "I will take this one and this one"!

Answer: The mother had never left the eggs from the moment she laid them until Levi sold them, so his Chatzer never acquired for him;

Shmuel instructed Levi to hit the nest, so the mother will jump up, allowing Levi to acquire, so he can transfer ownership of them to Rav Yehudah.

(Mishnah): One may not take a mother on her young even to be Metaher a Metzora.

Regarding Shilu'ach ha'Kan, an easy Mitzvah that entails a loss of about an Isar (the value of the mother), it says "Lema'an Yitav Lach v'Ha'arachta Yamim." All the more so this applies to difficult Mitzvos!

(Gemara - Beraisa - R. Yakov): Every Mitzvah for which the Torah writes its reward, it is (also) rewarded by Techiyas ha'Mesim.

It says about honoring parents "Lema'an Ya'arichun Yamecha u'Lema'an Yitav Lach";

It says about Shilu'ach ha'Kan "Lema'an Yitav Lach v'Ha'arachta Yamim."

Question: If a man asked his son to bring to him eggs from the top of a building, and the son (sent the mother and) took the eggs and died on his way down, where is the length of days and goodness that the Torah promises for these two Mitzvos?!

Answer: "Lema'an Ya'arichun Yamecha" must refer to the world (to come) that is eternal;

"U'Lema'an Yitav Lach" refers to the world (to come) that is all good.

Question: Perhaps (the reward is in this world, therefore) such an event would never occur!

Answer: R. Yakov saw such an event.

Question: Perhaps the son had sinful thoughts at the time (and was punished for them)!

Answer: Hash-m does not punish (Yisrael) for thoughts, only for sinful actions.

Question: Perhaps the son had idolatrous thoughts at the time! (Yisrael are punished for thoughts of idolatry.)

(Rav Acha bar Yakov): "Lema'an Tefos Es Beis Yisrael b'Libam" refers to thoughts of idolatry.

Answer: R. Yakov reasons that if the reward for Mitzvos were in this world, it should have saved him from having these thoughts that caused his death;

Rather, the reward for Mitzvos must be in the world to come.

Question: R. Elazar taught that harm will not befall someone on the way to do a Mitzvah!

Answer #1: He can be harmed on the way back.

Rejection: R. Elazar taught that harm will not befall someone on the way to do a Mitzvah or on the way back!

Answer #2: He went down a rickety ladder. The above law does not apply to dangerous situations;

Shmuel said "Eich Elech v'Shama Sha'ul va'Haragani" (he was concerned for danger, even though Hash-m told him to anoint David, which is a Mitzvah)!

(Rav Yosef): Had Acher (the Tana Elisha ben Avuya) expounded these verses like his grandson R. Yakov, he would not have become a heretic.

Question: What did he see that broke his faith?

Answer #1: He saw an incident like R. Yakov saw.

Answer #2: He saw the tongue of R. Chutzpis the translator (who was among the ten great Chachamim killed by Rome) in a wasteheap;

Acher was appalled that the tongue that spoke Torah so wondrously was not protected from such an end;

He did not know that "Lema'an Ya'arichun Yomecha" refers to the world that is eternal, and "u'Lma'an Yitav Lach" refers the world that is all good.