Agni said:
1-4. Ishall describe Vows (performed) on the seventh lunar day that would yield enjoyment and emancipation. One would be free from grief by worshipping Sun in the white lotus in the month of māgha (February-March). One would get everything by the worship of Sun on the seventh lunar day in the month of bhadra (pada) (September-October). The worship of Sun in the bright (fortnight) in the month of pausa (January-February) without taking food would destroy the sin. The seventh lunar day in the dark fortnight (in the month) of magha (February-March) would confer everything. The seventh lunar day in the bright fortnight in (the month of) phalguna (March-April) (is known as) nandāsaptami. (It confers benefit) by the worship of Sun. The seventh lunar day in the bright (fortnight) in (the month of) mārgasirsha (December-January (is known as) aparājita (unconquered). (It would make one so) by worshipping (Sun then). Women (who worship) on the seventh lunar day in the bright (fortnight) in (the month of märgaširsha (December-January) and for a year would get female children.
Summary of chapter 182 of the Agni Purāṇa is as follows:
The seventh tithi is declared to be especially sacred to Sūrya, and several solar vratas are described. Māgha-śukla-saptamī, the most auspicious Sūrya-saptamī, requires the worshipper to receive Sūrya's image on a lotus seat with water, arka-flowers, and red cloth. Bhādrapada-śukla-saptamī grants all desires; Pauṣa-śukla-saptamī is a pāpa-nāśana vrata. Among the kṛṣṇa-saptamī vratas, the Sarvāpti-saptamī and Nanda-saptamī are named. The Mārgaśīrṣa-śukla-saptamī called Putrīyā-saptamī is specifically recommended for women desiring a son, with Sūrya propitiated as the bestower of progeny.