According to Sri guru granth saheb ji
A person who worships God known bhagat.
The bani of bhagat, is before the birth of Sri guru nanak dev ji.
Known bhagat were lower caste hindus. They were prohibited not to worship God by hindus. Guru were only Brahmans they worship divines not a God.
Raja ram ki sev na kini keh ravdass chamara.
But after compiling adi garanth pancham patsah added to sikhs, satpurakh Jin jania satgur tiska nao.
Bani guru guru hai bani.