Why did she bring three bulls?
Radak: Some were to eat [as Chulin], and some were for Korbanos. This is why it says (verse 25) "they slaughtered the bull" (singular), i.e. the Korban.
Why did she take an Eifah of flour?
Rashi citing R. Yitzchak ha'Levi: An Eifah is three Sa'im, from which she would take three Esronim 1 of Soles (fine flour), the Minchas Nesachim for one bull. This is like a Mishnah (Menachos 76b) teaches - Lechem ha'Panim consists of 24 Esronim. Each Isaron is taken from a Se'ah of wheat.
Radak: Some was to eat [as Chulin], and some was for a Minchah.
An Eifah, Se'ah and Isaron equal are the volumes of 432, 144 and 43.2 eggs, respectively.
Why did she take wine?
Rashi: It was for Nesachim.
Radak: Some was to drink [as Chulin], and some was for Nesachim.
What is the meaning of "veha'Na'ar Na'ar"?
Rashi citing Targum Yonasan: The youth was Yanik. Radak - he does not mean that he was still nursing, for it says that she weaned him! In Arame'ic, Yanik is a young child. He was still very young and tender. Even so, she did not wait until he gets stronger. Rather, immediately after 24 months she brought him to Beis Hashem.
Radak: He was sharp, and knew [to distinguish] good from evil. This is like ha'Mena'er, one who shakes the waste off the flax.
Malbim: 'Na'ar' is from the verb Na'ar, like (Zecharyah 2:17) "Ki Ne'or mi'Me'on Kadsho" (to awaken). [A youth] is called a Na'ar, for then are aroused his natural powers and ethics to go from potential to actualization. Shmuel's intellect and Midos already began to develop even though he was just weaned. Chazal agreed to this, and said that he already taught a Halachah about Shechitah of the bull (that a Zar may slaughter Kodshim - Brachos 31b).
