Such is Satan’s envy and enmity against a Christian’s joy and comfort, that he cannot but act to the utmost of his strength to keep poor souls in doubt and darkness. Satan knows that assurance is a pearl of such price that will make the soul happy forever; he knows that assurance makes a Christian’s wilderness to be a paradise; he knows that assurance begets in Christians the most noble and generous spirits; he knows that assurance is that which will make men strong to do exploits, to shake his tottering kingdom about his ears; and therefore he is very studious and industrious to keep souls off from assurance, as he was to cast Adam out of paradise.
Thomas Brooks