“When a soul wishes to bring a meal-offering before Hashem…” (Leviticus 2:1)
Rashi points out that the term “soul” (nefesh) was not used in connection with any other voluntary offering but the meal-offering. This is because the meal-offering is the offering of a poor person – and to Hashem, even though it is a modest offering, it is considered as if they offered their very soul.