Vaisesika Sūtras
Vaisesika Sūtra 7.2.25
गुणैर्गुणाः ॥२५॥
guṇair guṇāḥ ॥25॥
[गुणैः (guṇaiḥ) - by qualities; गुणाः (guṇāḥ) - qualities;]
Qualities are by qualities.