Hilchot Berachot 2:7-8 (Additions to Birkat HaMazon for the homeowner and for a mourner)
8:08 pm
How many times must the concept of Divine kingship be mentioned in the fourth blessing of Birkat HaMazon? What extra line must be said by a guest in honor of his host? What additional words are added to the fourth blessing in a house of mourning?
