成唯識論述記 5.963

5.963

述曰：非於彼中可有婬事故，或無根，小地獄中可有此貪故。又若以為緣，故令其受苦，須彼一形者，即應一切定成二形。或復應彼一有情身罪極重者，有百千形令多，為彼受苦緣故。

The Commentary states: This is because sexual acts are impossible therein; or they are facultyless, because such greed is possible in minor hells. Furthermore, if having one gender were required as a condition to make them undergo suffering, then everyone would definitely possess both genders. Or, the body of a single sentient being whose offenses are extremely heavy should have hundreds of thousands of genders to make them numerous, serving as conditions for that being to undergo suffering.