If you eat a kezayis of bread you bentch. If you eat a seduah of pas haba bikisnin you also bentch.

If you ate slightly shy of a kezayis of bread and have only mezonos available, can you fill up the kezayis using mezonos or pas haba bikisnin food items?

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    Why would you think this works? You have fulfilled neither criteria. Please edit to explain.
    – Double AA
    Apr 15, 2015 at 17:15

1 Answer 1


r' moshe Feinstein in his responsa "iggros moshe" (exact source will be brought very soon! sorry!!) says that one may not, even for a rabbinic obligation, the reason being that the torah (and chazal) require a "ma'aseh achila" which only takes effect on a k'zayis, only once you have a ma'aseh achila of a k'zayis can other foods be used to complete a shiur of k'beitza and the rabbis ruled to recite bircas hamazon. in our case, again, there is nothing to be m'tzaref to, it isn't anything.

  • Welcome to Mi Yodeya, Michoel, and thanks for the answer! When you find the exact source, please edit it into your post. Hope to see you around. :)
    – Scimonster
    Apr 16, 2015 at 19:19

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