Shulchan Aruch (OC 167:18) says (in my own translation):
The one who slices the loaf of bread places a slice before each person. The individual then takes the slice with his hand. The one who slices the loaf does not put [the slice] into the hand of the one eating, unless [the latter] were a mourner.
Rama there explains that a mourner is customarily passed food (as is implied by a pasuk), and Mishna B'rura there (90) explains that therefore "it is inappropriate to do so when [the one eating] is not a mourner, lest his fate worsen".
My question is what precisely is indicative of mourning and therefore not done to non-mourners. Here are some options:
- Passing directly from the slicer to the eater is indicative of mourning. (However, passing it to a third party, who then passes it down the table to the eater, is fine, even if it goes from hand to hand throughout.) [This is literally what the Shulchan Aruch says.]
- Passing directly to the eater is indicative of mourning. (However, the slicer could pass it down the table hand to hand, as long as the last passage, to the eater, is not done from hand to hand.)
- Passing directly from the slicer is indicative of mourning. The slicer should not pass bread into someone's hand. (However, once the bread's on its way down the table, it can be passed hand to hand, even to the eater's hand.)
- Passing bread that will be eaten, from hand to hand, is indicative of mourning. Period. No one should pass bread to anyone.
(Of these, option 3 seems very unlikely to me, since the sources above make it sound like it depends on the eater.)
As an ancillary but closely related question: If option 3 or 4 of my four options above is true, i.e. if bread should not be passed to someone even if he's not the eventual recipient, then what happens if it is passed hand to hand? Whose fate can (lo alenu) worsen: the one who received the bread en route, or the eventual recipient? For example, say R'uven slices a slice for Levi and hands it to Shim'on, who places it in front of Levi. Levi then eats it. If my option 3 or 4, above, is correct, R'uven should not have handed the bread to Shim'on because someone's fate could worsen. Whose? (Of course, if my option 1 or 2 (or similar) is correct, then this second question is moot.)
Sourced answers would be ideal.