לה אין כי דדו בת אסתר היא הדסה את אמן ויהי” ובמות מראה וטובת תאר יפת והנערה ואם אב (ז ב אסתר) “לבת לו מרדכי לקחה ואמה אביה
Regarding the question from which age a small baby in Am Yisrael who passes away merits life in Olam Haba, the Tanna Rabbi Meir (Sanhedrin 110b) replies: “From when he says amen.” Therefore, the Rema rules (Orach Chaim 124 7): “And he should teach his young children to answer amen, because as soon as a baby answers amen, he has a share in Olam Haba.”
In light of this, Rav Eliyahu Hakohein of Izmir, author of Shevet Mussar, explained:
The passuk את הדסה“ says אמן ”ויהי – the omen is without a vav (Esther 2:7), to teach us that Mordechai taught Esther when she was very young to answer amen. And the passuk then explains that Mordechai did so “ki ein lah av v’eim”. Because Esther did not have a father or mother to teach her to answer amen, Mordechai took their place – “Vayehi omen es Hadassah.” (Minchas Eliyahu Ch. 31, Inyan Purim)
Sefer Notrei Amen (Vol. II, p. 279) it says on the words of the Shevet Mussar: “And we should pay attention to the wonderful fact that Mordechai and Esther, when they wrote the megillah with Ruach Hakodesh, saw it correct to write the word “אמן את הדסה” without the vav in order to teach us that the pure and holy chinuch that Esther received from Mordechai was by habituating her to answer amen.”
Notrei Amen further explains why Mordechai put an emphasis on this halachah: Because he saw that in the chinuch of answering amen, he would be able to imbue pure emunah in Esther’s heart, which would have the power to help her withstand any nisayon that would come upon her in her life. Indeed, Esther withstood many challenges that she encountered, and accepted the Din Shamayim with emunah in everything that happened to her.
Notrei Amen (ibid) further explained that Esther’s strictness to answer amen also protected her physically, in all the events that she experienced when taken to Achashveirosh’s house. This is what the Baalei Hatosafos mean (Tosafos Hashalem Esther 2:7) in their explanation of the words “Vayehi omen es Hadassah” as follows: “Amen is numerically equivalent to מלאך as if to say that an angel raised her.” In other words, those same angels that were created from Esther’s answering of amen are the ones that raised her and protected her every step of the way, as Chazal explain (Midrash Tehillim 31) the passuk (Tehillim אמונים נצר“ :)31:24 ה’” to mean those who are strict to answer amen.
