Bhakti initially flourished in South India through the great Vaishnava saints known as the twelve Alvars (6th-9th centuries). Shaivism also has its bhakti traditions and during roughly the same period 63 Nayanars (bhakti poets) wrote songs that now form the twelve books of the Tirumurai. Shortly after, and especially from 1500 CE onwards, a great devotional renaissance swept through the entire sub-continent. The bhakti saints largely rejected the hereditary caste system and its emphasis on prescribed ritual, stressing instead the need for morality, purity of heart and an attitude of selfless service. They expressed their sentiments through song, poetry and music, often attracting thousands of followers.