The ninefold devotion, Bhakti.

Hiranyakashipu asked his son Prahlada what he had learned from his teacher over the years. 

Prahalada replied: 

1. to hear (shravana) the glories of Vishnu,
2. to praise (kirtana) Him, 
3. to be absorbed in thoughts (smarana) of Him, 
4. to wait (seven) upon Him, 
5. to worship (archana) Him, 
6. to make one's prostration (vandana) to Him, 
7. to be his dedicated servant (dasya), 
8. to look upon oneself as His friend (sakhya), 
9. and to surrender (atmanivedana) oneself into His hand. 

If Devotion to Ishwara, which manifests itself in these nine ways, were taught to the pupil, and the pupil gave his full disinterested devotion to Ishwara, that would be the highest kind of learning.

~ Shrimadbhagvatam