Skandapurana 16.118.13

16.118.13

tasyaitāḥ śaktayo devi ṣoḍaśaiva prakīrtitāḥ ..
candrarūpī tataḥ kṛṣṇaḥ kalārūpāstu tāḥ smṛtāḥ .. 13 ..

These are proclaimed as his sixteen powers (śaktis), O goddess; / therefore Kṛṣṇa has the form of the moon, while they are remembered as having the forms of its digits.