Introduction
The eminent  scholar statesman Rajaji said “The way of devotion is not different from the  way of knowledge or Jnana. When intelligence matures and lodges securely in the  mind, it becomes wisdom. When wisdom is integrated with life and issues out in  action, it becomes Bhakti. Knowledge, when it becomes fully mature, is Bhakti.  If it does not get transformed into Bhakti, such knowledge is useless tinsel.  To believe that Jnana and Bhakti - knowledge and devotion - are different from  each other is ignorance.”
 
Narada Bhaktisutras is a popular and simple text containing 84 Sutras on Bhakti  or devotion. The date and authorship of this work are not quite clear though it  is generally ascribed to Devarshi Narada. He is typical in his Three-in-One  approach integrating Jnana, Karma and Bhakti into a single unified spiritual  experience. Although in their full maturity Jnana, Karma and Bhakti merge into one  another; in the early stages they do appear to be different methods to reach  the Absolute. He deals with Bhakti as the easiest and most efficient of all the  paths or Yogas available to everybody irrespective of caste, creed, color or  sex.
 
All the three spiritual paths lay down the one condition of purity of mind,  with its functions of intellect, emotion and will having been cleansed of the  muck of Ego for knowing the Godhead. Jnana Yoga purifies the intellect, Karma  Yoga the will and Bhakti Yoga the emotions. The seeker is free to adopt any one  of these according to his interest and temperament. But he would do well to  attempt a synthesis of all these three paths for achieving the end more  effectively. We find in the Narada Bhakti Sutras which primarily deal with  Divine Love that the author achieved a happy synthesis of all the three Yogas  treating them all as aides to achieve the final goal, as was done by the  Yogeswara, Sri Krishna in the Bhagavad Gita.

Sutra or  aphorism means a cryptic statement containing vast ideas within the compass of  a very few words. A sutra also means a thread or a string - a support
  - in which great ideas are strung together like flowers in a garland or pearls  in a necklace.

Although the  original text does not contain any divisions it is grouped here under different  sections for a smooth thought-flow.

Nature of Divine Love (Sutra 1)
Any study of  spiritual practices can appeal only to those who have an intense desire for  knowing the subject coupled with deep faith in the teacher and the scripture  whose help he seeks. While each scripture prescribes certain specific  qualifications for attaining the goal, the scriptures of Bhakti declare that  the path of Divine Love is open for all. A belief in the grace of God and faith  in the possibility of escape from the cycles of birth and death with the help  of God is the only qualification required for the study of Bhakti Sutras and  the practice of Divine Love. 

Bhakti can lead  to God-Realization and escape from Samsara as an independent means all by  itself. It is the easiest of all paths available to any one. It is of help even  to those who aspire for Jnana for the sake of maintaining their loving  relationship with God.
This may probably be the reason that prompted Narada to write on Bhakti in  preference to Jnana or Karma. These Sutras or aphorisms should be construed not  as a commentary on Bhakti as a speculative philosophy based on reason but as an  exposition on the author’s actual personal experiences, supported by  scriptures.

Definition of Bhakti (Sutra 2 & 3)
The term Bhakti  comes from the root ‘Bhaj’, which means ‘to be attached to God’. Bhakti is  divided into two types viz. Apara Bhakti or Gauna Bhakti and Para Bhakti. Apara  Bhakti is the initial stage of devotion of an aspirant in the path of Bhakti  while Para Bhakti is the highest stage in that path.

Bhakti Yoga is  the path of loving devotion to God. It is expressed by means of ritual worship,  prayer and japam. It is the cultivation of a direct, intense personal  relationship between the worshipper and the worshipped. In the practice of  Bhakti Yoga some special aspect of God or some Divine incarnation is chosen so  that the devotee’s love may become more easily concentrated. For those who are  naturally drawn to this approach, it is the simplest of all. There is no doubt  that the great majority of believers, in all the world’s major religions, are  fundamentally Bhakti Yogis.

Bhakti can be  defined as an exclusive love for God, love for love’s sake. The devotee, with  indifference to the pleasures and affairs of the world and no selfish  expectation, reward or fear, wants God and God alone. Faith in God, attraction,  adoration, suppression of mundane desires, single-mindedness and attachment are  the stages through which the devotee develops the supreme love towards God. At  the last stage of Bhakti (supreme love - Para Bhakti) all sensory attractions  towards objects of enjoyment are transferred to the only one dearest object  viz. God. It is an eternal union of the devotee with his beloved culminating in  oneness between the two. The devotee drinks the real nectar of supreme devotion  securing freedom from the wheel of births and deaths. 

We can appreciate the experience of this love by  looking at the following statement of Hanuman to Sri Ram. “When I think of  myself as an embodied being, I am your servant; when I think of myself as an  individual soul, I am part of you; but when I realize ‘I am Atman’ I am one  with you. This is my firm conviction.”