From All About Hinduism — Swami Sivananda — Navratri


... Outwardly, the nine days' worship of Devi, or the mother, known as Navaratri Puja, is in the nature of a vijaya-utsava [victory festival]. The nine days' triumphs are offered to the mother for her successful struggle with the formidable demons led by Sumbha and Nisumbha. But, to the spiritual aspirant in his life of sadhana, the particular division of the Navaratri into sets of three days to adore different aspects of the supreme goddess has got a very sublime, yet thoroughly practical, truth to reveal. In its cosmic aspect, it epitomizes the stages of the evolution of man into God, from jivahood to Sivahood. In its individual import, it shows the course that his spiritual sadhana should take...