The line is from “America: A Prophecy” (1793). It’s spoken by Boston’s Angel, who is raging against hypocrisy and injustice:
“What God is he, writes laws of peace, & clothes him in a tempest / What pitying Angel lusts for tears, and fans himself with sighs / What crawling villain preaches abstinence & wraps himself / In fat of lambs?”
The “God” here is not a named deity — it’s a rhetorical question. Blake is asking what kind of God would prescribe peace yet wrap himself in a storm, i.e., a hypocritical, authoritarian god who preaches one thing and enforces another. It’s consistent with Blake’s broader critique of the Jehovah figure from orthodox Christianity, whom he saw as a tyrannical, vengeful lawgiver rather than a merciful one. The passage is part of the Angel’s rebellion — he tears off his robe and throws down his scepter in defiance.