Skandapurana 2.4.37.14

2.4.37.14

13 satyabhāmākṛṣṇasaṃvāde satyabhāmāyāḥ pūrvajanmani kātikavratapuṇyena kṛṣṇabhāryātvaprāptirjāteti varṇanama, sarveṣāṃ madhye kārtikaḥ pravaraḥ kathamiti pṛṣṭena kṛṣṇena satyabhāmāṃ prati śaṃkhāsurākhyānena kārtikapravaratvanirūpaṇam, prayāgasthānamāhātmyama. 166 1

13. In the dialogue between Satyabhāmā and Kṛṣṇa, the description of Satyabhāmā attaining the status of Kṛṣṇa's wife by the merit of the Kārtika observance in her previous birth; when asked how Kārtika is foremost among all [months], Kṛṣṇa's determination of Kārtika's supremacy addressed to Satyabhāmā by means of the story of the demon Śaṅkha; the māhātmya of the sacred site of Prayāga. 166 1