Mother should be bathed with Ganges water

Maa Durga should be bathed with Ganges water on the day of Ashtami. Because the fair colour of the Gauri mata was obtained only by bathing in the Ganges. Legend has it that after severe penance, when Lord Shiva was pleased with Mother Parvati, she asked him to take a bath in the Ganges. As soon as the mata took a bath in the Ganges, one form of her appeared with a black colour, which was called Kaushiki and the other form was called Mahagauri. Therefore, it is considered best to bathe Goddess Durga with Gangajal on this date. By doing this, the special grace of Maa Durga is obtained.
If you do the recitation of Durga Saptashati in this way, you will get virtue and benefit.