Firstborn sons and firstborn donkeys belonged to Yahweh, but Yahweh did not want them sacrificed to Him. Instead, the Israelites were to sacrifice a lamb in their place. This allowed the Israelites to “buy” the donkeys and sons from Yahweh.
"no one may come to me without an offering." AT: "Every person who comes to me must bring an offering" (See: [[rc://en/ta/man/translate/figs-litotes]])