Chabad.org — English translation + Rashi
Torah Temimah points to Toras Kohanim (Sifra) on 3:7.
Sefaria — Sifra / Toras Kohanim
English: “If a sheep” — to include the pesach.
Ribbuy of the pesach under sheep shelamim rules — the pesach is included in the procedures stated for a sheep.
The pesach is included in the procedures stated for a sheep. The Sifra treats the phrase “if a sheep” as deliberately broad enough to encompass the pesach animal when it is brought under the rubric of shelamim. The result is that certain sacrificial details that apply to the ordinary sheep shelamim are extended to the pesach as well.