Numbers 8:16

Instead of such as open every womb, even instead of the firstborn of all the children of Israel. — It is difficult to determine whether the second clause is to be regarded as an exact equivalent, or as a limitation of the first. If an exact equivalent, a different meaning must be assigned to the firstborn from that which it commonly bears in the Pentateuch, where it appears to be restricted to the firstborn son on the father’s side. (Cf. Exodus 13:2.)