The Mishnas Chassidm wrote:
When the mevarech hears amen being answered by the oneh (see Rema Orach Chaim 167 2), it is as if he also answered amen after his brachah, because a "shomea k’oneh", one who hears is like one who answers. So we find that with every answering of amen to a brachah, there are at least two who answer amen – the mevarech and the oneh. For this reason, Chazal say (Shabbos 119b) on the passuk (Yeshayahu 26:2): "Pischu she’arim veyavo goy tzaddik shomer emunim," – "do not read it shomer emunim, but rather she’omrim amen." They used the plural of "she’omrim" and not "she’omer amen." This alludes to the fact that every answering of amen to a brachah has at least two "she’omrim amen," the mevarech and the oneh. (Aderes Eliyahu Shabbos ibid)
This is what Dovid Hamelech intended when he said (Tehillim 34:2): "Avarchah es Hashem bechol eis tamid tehilaso befi: answering amen is called ‘tehillah’ as Chazal say (Tosefta Brachos 6:22) on the passuk (Nechemiah 9:5): "Umeromam al kol brachah usehillah" – that for every brachah that is heard, the listener needs to give a "tehillah" to Hashem, by answering amen. That is what Dovid said: "Avarchah es Hashem bechol eis" – with a brachah, and when I hear the amen that is answered after my brachah, then as a shomea k’oneh, it is as if "tehilasso befi", his praise is in my mouth. (Chazah Tzion Tehillim ibid)
Dovid Hamelech Answered Amen
The final words of the letters of the passuk (Tehillim 57:3): "אקרא לאלקים עליון"– is amen. And the Mishnas Chassidim explained that this is what Dovid alluded to in this passuk: Each time I hear a person calling to Hashem with a brachah, and by doing so, crowns Him as the Highest above all, I am careful to answer amen after him (Chazah Tzion, Tehillim ibid).
Mishenichnas Adar marbim Besimchah
The holy Zohar (Vayeilech 285 2) says that in the merit of answering amen with kavanah, the gates of brachah and goodness On High are opened, and simchah is aroused in the all the worlds, and he writes: "And when Am Yisrael in this world are careful to answer amen...how many openings of brachah are open to them On High, how many good things are found in all the worlds, how much simchah is in every place."
