בא מהרתן מדוע ויאמר אביהן רעואל אל ותבאנה” (יח ב) “היום
In Maseches Brachos (47a), Chazal determine that the life of a person is contingent on answering amen slowly. They say: “Anyone who prolongs the amen has his days and years lengthened.” In contrast: “One who answers a short amen – has his days shortened.” (The punishment of one who answers a shortened amen does not appear in this Gemara, but the Rishonim hold that it is so in the Gemara, and see Tur Orach Chaim 124.)
The “one who prolongs his amen” is someone who answers amen slowly, as is fitting, which means as long as it takes to say ‘Kel Melech Ne’eman.’ He should take care, however, not to answer an amen that is too long, because when one prolongs the amen too much, then he takes it out of context, as the Shulchan Aruch rules (Orach Chaim 124 8): “And he should not answer a short amen, but rather a bit of a longer one, with enough time to say: Kel Melech Ne’eman, and he should not prolong it too much because then the word is not heard.”
The Mishnah Berurah (ibid 36) explains when one answers amen quickly this manifests a laxity in the mitzvah, as the oneh says it as if it is a heavy burden that he is seeking to absolve himself of.
The obligation to answer a longer amen is alluded to in this passuk: מהרתן בא היום– the last letters comprise אמן. So the passuk is seeming to ask us: Why did you hurry to answer amen, and by doing so you failed by answering a shortened amen and you lost the merit and the reward of one who answers a long amen?!
