Shaarei Gan Eden
Amen and Brachos in the Teachings of a Baal Hayahrtzeit
In one of his shmuessen, the Mashgiach Rav Dessler said that from the reward promised to those who answer amen, we can learn about the significance of every word that we utter. He said:
In Maseches Nedarim (32a) it is brought that Avraham Avinu was punished that his children were enslaved by Mitzrayim because when HaKadosh Baruch Hu promised him the land, he asked for a sign of confirmation of this promise, when he said (Bereishis 15:8): "Bemah eida ki irashenah."
Here we find that for saying two words that sounded like a violation of Kavod Shamayim, our fathers were sent to terrible slavery for 210 years in Egypt. Two words rendered the fate of Bnei Yisrael to a prolonged and difficult exile.
For some reason, we tend to think that only the words that Avraham Avinu uttered have such significant consequences but that is not the case. We have to know that every word that we utter, and every small deed that we do, has tremendous significance.
Let’s take the mitzvah of answering amen, for example, of which Chazal say (Shabbos 119b) "Anyone who answers amen with all his strength has the gates of Gan Eden opened for him." Chazal revealed to us that every Yid, in every situation that he is in, when he stands and answers amen with kavanah, he merits tremendous reward for that – to have all the gates of Gan Eden opened for him. Although answering amen is a simple action that does not require special sacrifice, still, the reward that a person receives for it is immeasurable.
Shaarei Hashmanim, Chanukah p. 208