Rashi on Leviticus 3:7/רש"י על ויקרא ג׳:ז׳

1אם כשב IF [HE OFFER] A LAMB — Because there is amongst the fat-portions of the lamb something which is not amongst the fat-portions of the goat, — for of the lamb the fat-tail (אליה) is offered, — therefore they (the law regarding the lamb and that regarding the goat) have been divided into two separate paragraphs (whilst in the case of the free-will עולה they are contained in one paragraph, Leviticus 1:10—13, since there is no difference in the laws regarding these two animals) (cf. Sifra, Vayikra Dibbura d'Nedavah, Chapter 18 4).