The Torah does not inform us that Moshe divided the blood into two. Who divided it?
Rashi: An angel came and divided it.
What is the significance of the division of the blood?
Hadar Zekeinim: It is the way that one enters into covenants, as we find by the B'ris Bein ha'Besarim - in Lech-L'cha Bereishis, 15:10 and in Yirmiyah, 34:18.
What were the "Aganos" into which Moshe placed the blood?
Rashi: They were bowls into which he placed half the blood, one for half the blood of the Olos; the other, for half the blood of the Shelamim - to sprinkle on the people. 1
Ramban #1: They were receptacles made not in the shape of the regular Mizr'kos (the bowls that were generally used on the Mizbe'ach), which were used to sprinkle on the people. 2
Ramban #2 (citing the Ibn Ezra and Targum Onkelos) and Targum Yonasan: Moshe used the regular basins to sprinkle both on the people and on the Mizbe'ach.
Incidentally, we learn from here that Korbanos require a K'li - See Rashi in Pinchas, Bamidbar 28:6.
To sprinkle the other half of the blood on the Mizbe'ach, Moshe used regular Mizr'kos (Ramban).
Why did Moshe sprinkle half the blood on the Mizbe'ach?
Rashi: Refer to 24:6:3:1.
Seforno: He appointed the Mizbe'ach as the Shali'ach of Hashem, and the blood that was due to be sprinkled on Hashem (Kevayachol) in His capacity as the other side entering into the covenant, he sprinkled on the Mizbe'ach.
Kerisus, 9a: This teaches us that Yisrael entered into the covenant with the sprinkling of the blood.
What is the significance of the sprinkling of the blood on the people?
QUESTIONS ON RASHI
Rashi writes that an angel divided the blood. Why was this necsessary - seeeing as we hold that it is possible for a person to be precise?
Rosh and Moshav Zekenim: The angel divided the blood while it was still inside the animal, something that only an angel can do. 1
Moshav Zekenim: The angel closed the place of Shechitah of each animal after exactly half the blood left, and after Moshe sprinkled the first half, the angel opened the wound, and Moshe collected the latter half.
Rashi writes that our fathers entered into the covenant with Milah, Tevilah and Haza'ah. But the Gemara in Yevamos 46a states that our fathers circumcised, but did not Tovel?
Riva: There, The Gemara is referring - not to our fathers in Egypt, but - to Avraham, Yitzchak and Ya'akov, who did not Tovel.
Tosfos Yeshanim (in Yevamos 46a): The Gemara is going according to R. Eliezer, who holds that the blood was sprinkled on the Mizbe'ach to atone for the people, wwhereas Rashi's commen follows the opinion of R. Yehoshua, who holds that half the blood was sprinkled on the people, in which case they must have Toveled.
