The Parsha describes the mitzvah of challah, the act of separating a piece of kneaded dough and donating it to the priest (15:17-21), distinct from the commandment to donate grain (Terumah). Why is this dough double-taxed (taxed first as grain and then as dough)?

Rav S. R. Hirsch posits that while donating grain exhibits our appreciation for the assets we’ve attained, the mitzvah of challah represents our efforts associated with those resources. Challah is created through man-made efforts, unlike grains which grow naturally. So too, to be in a position where our efforts matter is just as much of a blessing. Challah demonstrates this recognition that not only do our resources need to be shared, but also our efforts.