Simon Brittan discusses the idea of poetry being "divinely inspired" in his book Poetry, Symbol, and Allegory: Interpreting Metaphorical Language from Plato to the Present. He says that if all things are "symbols" for God, if God is in everything, then the world is an allegory for the original creation. Brittan explains that "Blake sees all religions as one because they all attempt to speak, though in different accents and using different grammars, about the same physical world." I think this is the key idea that Blake is expressing in his poem. All men "are alike in outward form" and are essentially praying to the same Being or God, and thus are all interconnected in this way.
Source: Poetry, Symbol, and Allegory: Interpreting Metaphorical Language from Plato to the Present
Source: Poetry, Symbol, and Allegory: Interpreting Metaphorical Language from Plato to the Present