Here is what the Kollel wrote on the question that you raised in our "Insights to the Daf." I hope you find it enlightening.

Best wishes,

Mordecai Kornfeld

==============================================================

From Insights to the Daf, Nazir 66

(d) RAV YISRAEL AZOR shlit'a proposes that the Gemara here answers the question posed by the RADAK in the beginning of Sefer Shmuel (Shmuel I 1:11). Rebbi Nehora'i maintains that Shmuel was a Nazir because his mother made an oath that the child would be a Nazir when she said, "Morah Lo Ya'aleh Al Rosho." Why was her declaration a binding oath of Nezirus for her son? The Mishnah earlier (28b) clearly states that a father can make his child a Nazir but a mother cannot! (See GILYON HA'SHAS there.) If, on the other hand, Chanah told her husband, Elkanah, that she wanted Shmuel to be a Nazir and she asked him to make the child a Nazir after he was born, why does the verse make no mention of his oath of Nezirus for the child? The verse mentions only her declaration of Nezirus, which was not binding. (The Radak wonders why Chazal themselves do not ask this question.)

Rav Yisrael Azor explains that the Gemara here addresses this question as follows. The Mishnah earlier (20b) teaches that if a woman says to her husband, "I am a Nezirah and you are," and her husband says "Amen," he becomes a Nazir as a result of his consent to the Nezirus which his wife accepted on his behalf. The Gemara suggests that Chanah told Elkanah that the child will be a Nazir and Elkanah said "Amen" to her oath. Since he said "Amen," her Neder took effect.

Why, though, does the verse make no mention of Elkanah's role in the Nezirus? The reason why the verse mentions only Chanah's role, and not Elkanah's, in the acceptance of Nezirus for their child is the same reason why the Torah relates that Tziporah performed the Bris for her son and makes no mention of Moshe Rabeinu in the incident (Shemos 4:25). The Gemara in Avodah Zarah (27a) asks whether the verse proves that a woman may perform Milah to her son. The Gemara answers that the verse is no proof because perhaps Tziporah merely began the Milah and Moshe Rabeinu finished it, and the verse merely attributes the act to her since she initiated it (even though the fulfillment of the Mitzvah is attributed to the one who completes it). In the same way, since Chanah initiated the acceptance of Nezirus for her son, the verse attributes it to her even though it was her husband who made it binding.

This answers the Radak's question, why Chazal do not ask how Chanah was able to accept Nezirus on behalf of her son. The answer is that the Gemara does address this question when it discusses the topic of responding "Amen" to a blessing, immediately after the Mishnah which says that Shmuel was a Nazir. The Gemara presents an opinion that it is more preferable to recite a blessing than to say "Amen" to one -- which may be inferred from the fact that the verse mentions only the oath that Chanah made and does not mention that Elkanah answered "Amen" after her oath, an indication that the one who initiates the blessing (or declaration) is greater.