- Question: [Sunday 29th Sivan 5780]
What should be done if one began Kaddish without a Minyan? What if the person refuses to stop, should you still answer?
The person must stop reciting the Kaddish if there was no Minyan to begin with, when he initially began saying it. If he does not stop, then no one in the congregation should answer Amen etc. When the tenth man arrives, he should then repeat it from the beginning. If, however, he began Kaddish with a Minyan and the Minyan then left, then he may continue, and one is to answer, as brought in the Talmud Yerushalmi, and Poskim.
The reason: As its forbidden to say a Davar Shebekedusha without a Minyan as evident from all Poskim, and brought in Noda Beyehuda, and one who does so is logically required to stop in middle, as rules Birchas Habayis. Furthermore, one should be required to repeat it from the beginning once a Minyan arrives, unlike the seeming Chidush of the Noda Beyehuda, which is questioned by the Shevet Halevi, and is said only regarding the repetition of blessings due to Bracha Levatala. And hence by Kaddish, of which there is no such Chashash, certainly it is to be repeated from the beginning.
Sources: See Admur 55:2-3; Birchas Habayis 42:6; Noda Beyehuda Kama E.H. 56; Shevet Halevi 4:14; Piskeiy Teshuvos 55:1