Was Kabir a weaver?

Yes, Kabir was a weaver by profession. He became a disciple of Sant Ramananda of Banaras, who was an exponent of the nirguna school of bhakti that lays stress on the impersonal aspect of the One Lord.

For further reading check the following articles:

• Difference Between Sufi and Bhakti Movements
• Sufism in India