How should we fast during Navarātri?

as your health and family custom allow — all nine days, or the first and last days — with daily worship of the Devī.

Navarātri, the nine nights of the Goddess, comes twice a year in most homes: Caitra (spring) and Śārada or Āśvina (autumn). Many families begin with ghaṭa-sthāpanā, installing a sacred pot, on the first day and sow barley (jau or jawāre) beside it.

Fasting styles vary widely. Some keep all nine days on phalāhāra, eating once a day; some fast only on the first day and Aṣṭamī; many simply give up grains, onion, garlic and non-vegetarian food for the nine days. In Bengal, Durgā Pūjā is a festival of feasting rather than fasting, and in Gujarat the nights are for garbā. All are authentic.

The vrata usually closes on Aṣṭamī or Navamī with kanyā-pūjana: young girls are honoured as forms of the Devī, their feet washed, and they are fed and given gifts. Then the fast is broken with prasāda.

Source: Devī Bhāgavata Purāṇa; regional custom · Kanyā-pūjana on Aṣṭamī or Navamī

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