89. Kaddish
15:5 One should make sure to hear the Kaddish and to reply to it with proper concentration, especially to “Amen, y’hei Shmei rabbah,” the proper recitation of which can annul a negative Heavenly decree of even 70 years. This response should be said out loud because it is the sound of one’s voice that cancels out the stern decrees. However, it should not be said so loud that it would cause others to mock him. (One may not even learn Torah while Kaddish is being recited – Mishnah Brurah 56:1. Answering “Amein y’hei Shmei rabbah is even more important than answering Kedusha – MB 56:6.) “Amen y’hei Shmei rabbah” is recited with the word “yisbarach,” after which we listen to the one saying Kaddish and we reply “Amen.” (The Gra says we do not tack “yisbarach” on to the end. While there are different opinions, if the one answering is in a place in davening where he may not interrupt, he should follow the opinion of the Gra – MB 56:15.)
15:6 Every Kaddish that follows a prayer which is recited while standing, such as Hallel, is likewise recited standing. Regarding other Kaddishes, there is a difference of opinion. It is advisable to follow the more stringent view and to stand for Kaddish and all other “matters of holiness.” If Eglon, king of Moab stood up for the word of God (as we see in Judges 3:20), we should certainly do so!