Guru Grantha Sahib, sacred book of the Sikhs contains four poems of Trilochan, 62 of Namadeva and 240 Sakhis and 227 padas of Kabir. Most of the characteristic teachings of Sikhism like monotheism, crusade against idolatry and caste, externalism (bhaiachara), ritualism could be easily traced to these saint poets, especially Kabir. Kabir appears to be a contemporary of Guru Nanak.
Guru Grantha Sahib for the Sikhs is what the Bible is to the Christians, the Quran to the Muslims, the Veda to the Brahmins. It contains Bani that stands on the same level as 'the Word' of the Christians, 'Shabd'of the Brahmas and Saivites. Guru Nanak himself had composed a number of songs. The best among them are named Japji, Asa-di-var, Rahi-rasa Patti, Dakani Omkara, Siddha Gosthi and Bara Mah.
Other Gurus after Guru Nanak have also added their compositions in the sacred book. Guru Grantha Sahib was composed in 1604 by Guru Arjan Dev with assistance of one of the great devotees by the name Bhai Gurdas. It was written in Gurmukhi Script so that the Sikhs may remain Guru-centred. Guru Grantha Sahib includes not only the compositions of Gurus but also of many Saint poets. It includes verses of Ramanand, Jaideva, Namadeva, Trilochan, Veni, Dhanna, Pipa, Sain, Kabir, Rai Das, Shaikh Bhikhaji, Sadhna, Surdas, and Poona Nane and also some of Muslim Sufis.
However, the compositions of Kabir are far more numerous than any other non-Sikh composers. It includes 243-245 Sakhis and 227 padas of Kabir." This shows the great esteem in which Sikh Gurus held Kabir. Kabir was a non-Vedic Hindu influenced by Gorakhnath and some Buddhist poets.
Hence, much of Sikhism has to be understood and interpreted in terms of Saint's religious philosophy. However, Sikhism in course of its historical development has to be understood as an independent religion like Jainism and Buddhism. But it is considered as an Indian religion and is wholly embedded in the culture and tradition of India. It is more non-Vedic than Vedic.