Part 14: Rosh Hashana and Pesach
The source of the saying, “that we be a head and not a tail”, “And the Lord will set you at the head and not at the tail” (דברים כח יג), does not associate God’s blessing with eating a certain food but with doing God’s will.
All foods used on Rosh Hashana can be plants. Some Sephardic communities will not eat fish on Rosh Hashana and the Rashbatz said that it is wrong to eat fish (כך מביא החיד”א והבן איש חי). “While we’re asking the heavens to have mercy on ourselves and our families, it is only proper that we would show mercy for God’s creatures.” The fish head can be replaced with any vegetable (such as a head of lettuce) and the bee honey can be replaced with date honey, which is what the Torah means when it refers to honey.
For Pesach, using an egg and a shank bone is a custom and not a mitzvah and any cooked vegetables may be used.
“The Talmud asks: What are these two cooked foods mentioned in the Mishna? Rav Huna said: Beets and rice. The Gemara relates that Rava would seek beets and rice for his meal on Passover night, since this ruling came from Rav Huna’s mouth. Although Rava realized that Rav Huna was merely citing examples and did not mean that one must eat those specific foods, he wanted to fulfill the statement of his teacher precisely.” (פסחים, קיד ע”ב)
To summarize, there is no instruction or mitzvah to use a fish head on Rosh Hashana, or an egg and a shank bone on Pesach. These are customs.