Ibn Ezra on Leviticus 6:22

וטעם קדש קדשים הוא. עם כל זכר שאין ראוי לאכול החטאת שהקריבו ממנה והובא לכפר כי אם התמימים והזכר תמים מהנקבה ואפילו קטן יקרא זכר והזכר שהוא בן שלש עשרה שנה כאשר העתיקו אבותינו: [IT IS MOST HOLY.] Scripture states it is most holy with regard to every male⁷⁴Scripture states that the sin offering is most holy in verse 18. The question thus arises, Why repeat it again in our verse? because only the perfect may eat from a sin offering whose organs are offered and is brought for atonement for sins.⁷⁵Scripture repeats it is most holy with regard to all male kohanim in order to teach us that only the “perfect” may eat from the sin offering because it is most holy. Males are more perfect⁷⁶I.E. believed that males are superior to females. than females.⁷⁷No female may eat from the sin offering. Even a small child is called a male.⁷⁸In other words, a male under the age of 13 may eat of the flesh of a burnt offering. A male who is thirteen years old [is considered an adult] as our fathers have transmitted.