Ibn Ezra on Leviticus 4:35

וטעם כאשר יוסר חלב הכשב. להביא האליה כי אין עם השעירה אליה: [AS THE FAT OF THE LAMB IS TAKEN AWAY.] Scripture states the aforementioned because it wants to indicate that one is to offer the fat tail,⁵⁵When a lamb is offered. for a she-goat has no fat tail.⁵⁶Hence Scripture omits the law of the fat tail when it deals with the offering of a she-goat, which does not have a fat tail.