The feeling of Bhakti or devotion can be traced back to the Rig Veda. It is the very first hymn of the Rig Veda, which gives expression to a feeling of intimacy with the highest god. In the Katha Upanisad it is said that the divine help, which is the reward to Bhakti, is necessary before one can be saved. The Svetasvatara Upanishad speaks of the highest devotion to God. Panini refers to the object of devotion in the Astadhyayi. The earliest god connected with bhakti is Vishnu-Krishna. In the Bhagavadgita there is emphasis on love and devotion to God. The attitude of love to the Supreme God continued to be recommended in the Bhagavata Purana.

Characteristics of Bhakti Movement
One chief characteristic of the Bhakti movement can be mentioned as belief in one God. A devotee could worship God by love and devotion. The second characteristic of the Bhakti movement was that there was no need to worship idols or to perform elaborate rituals for seeking his grace. The third feature on which the Bhakti saints laid stress was the equality of all castes. There was no distinction of high or low as far as the devotion to God was concerned. The fourth feature was the emphasis, which these saints laid on Hindu-Muslim unity. According to these saints all men irrespective of their religion are equal in the eyes of God.

The saints preached in the language of the common people. They did not use Sanskrit, which was the language of the cultured few. These saints laid stress on purity of heart and practice of virtues like truth, honesty, kindness, and charity. According to these saints only virtuous man could realize God. These saints considered God as omnipresent and omnipotent. Even a householder could realize God by love and devotion. Some saints regarded God as formless or Nirguna while others consider him as having different forms or Saguna.

Factors that helped the development of the Bhakti movement
There were a number of factors, which contributed to the rise, and growth of the Bhakti movement during the medieval period. The first important factor was the destruction of Hindu temples by the invaders. They destroyed idols of Hindu gods and goddesses. The Hindus lost faith in the dependability of their religious rites and, therefore, chose the path of love and devotion.

The second factor can be presumed as the persecution of Hindus by the Muslim rulers, who tried to convert them to Islam and imposed jaziya if they were not prepared to become followers of Islam.

The third factor was the ill treatment of the lower classes in Hindu society by the persons of upper castes. The people of the lower castes had to suffer injustice and cruelties. So the teachings of the Bhakti saints who preached equality of castes as far as the devotion to God was concerned appealed to the people of lower castes.

Indian Bhakti Preachers
There are some personalities that are known as the saints of Bhakti movement and they are widely respectable.

Ramanuja
The first great exponent of Bhakti was Ramanuja. He lived in the eleventh century. He asked his followers to worship Vishnu. He did not believe in Sankara`s Advaita doctrine according to which the universal soul and the individual souls are one. According to Ramanuja the individual souls exhale from him but are not essentially one with the Supreme Reality.

Ramananda
Ramananda flourished in North India in the fourteenth century. He entirely discarded the theory of caste system by birth. He preached the worship of Rama and Sita. Persons of all castes became his disciples. Among his chief disciples there was a barber, a chamar and a weaver. He preached in Hindi, which was the language of the common man in northern India.

Kabir
The life of Kabir is totally unknown to the humankind. A true proponent of the Bhakti Movement Kabir was a holy soul who further preached about the unity of Hindu and Muslim.

Guru Nanak
Nanaka was born in 1469 in the village to Talwandi. Presently the place is known as Nankana in the Sheikhupura district of West Punjab. His parents belonged to Khatri caste. His father Kalu was the Patwari of the village. Nanaka was educated in the village school.

Vallabhacharya
Vallabhacharya was a Tailang Brahmin. He preached the worship of Vishnu in the form of Krishna. He was born in 1479 in the Telugu country. He visited Mathura, Vrindavan and many other sacred places and finally settled at Varanasi.

Chaitanya
Chaitanya was the greatest saint who preached the worship of Krishna and Radha. Chaitanya was born at Navadwipa in 1486. His father Jagannatha Misra was a religious and scholarly man and his mother Sachi was also a pious and religious minded lady.