Numbers 18:15-19

18:15 The firstborn of every womb which they present to the Lord, whether human or animal, will be yours. Nevertheless, the firstborn sons you must redeem, ¹  and the firstborn males of unclean animals you must redeem. 18:16 And those that must be redeemed you are to redeem when they are a month old, according to your estimation, for five shekels of silver according to the sanctuary shekel (which is twenty gerahs). 18:17 But you must not redeem the firstborn of a cow or a sheep or a goat; they are holy. You must splash ²  their blood on the altar and burn their fat for an offering made by fire for a pleasing aroma to the Lord. 18:18 And their meat will be yours, just as the breast and the right hip of the raised offering is yours. 18:19 All the raised offerings of the holy things that the Israelites offer to the Lord, I have given to you, and to your sons and daughters with you, as a perpetual ordinance. It is a covenant of salt ³  forever before the Lord for you and for your descendants with you.”

¹ tn The construction uses the infinitive absolute and the imperfect tense of the verb “to redeem” in order to stress the point – they were to be redeemed. N. H. Snaith suggests that the verb means to get by payment what was not originally yours, whereas the other root גָאַל (ga’al) means to get back what was originally yours (Leviticus and Numbers [NCB], 268).

² tn Or “throw, toss.”

³ sn Salt was used in all the offerings; its importance as a preservative made it a natural symbol for the covenant which was established by sacrifice. Even general agreements were attested by sacrifice, and the phrase “covenant of salt” speaks of such agreements as binding and irrevocable. Note the expression in Ezra 4:14, “we have been salted with the salt of the palace.” See further J. F. Ross, IDB 4:167.