Read this tonight:

Reason testifies that Divine Love is so essential in Religion that all Religion is but hypocrisy and a “vain show” without it. What is Religion but the exercise and expressions of regard to the Divine Being? But certainly if there be no love to Him, there is no sincere regard to Him; and all pretences and show of respect to Him, whether it be in word or deed, must be hypocrisy, and of no value in the eyes of Him who sees the heart How manifest is it that without love there can be no true honour, no sincere praise! And how can obedience be hearty, if it be not a testimony of respect to God! The fear of God without love is no other than the fear of devils; and all that outward respect and obedience, all that resignation, that repentance and sorrow for sin, that form in religion, that outward devotion that is performed merely from such a fear without love, is all of it a practical lie, as in Psalm 66:3– “…How terrible art Thou in Thy works! through the greatness of Thy power shall Thine enemies submit themselves unto Thee.” In the original it is “shall thine enemies lie unto Thee” — i.e., shall yield a feigned or lying obedience and respect to Thee, when still they remain enemies in their hearts. There is never a devil in hell but what would perform all that many a man [has] performed in religion, that had no love to God; and a great deal more if they were in like circumstances and the like hope of gain by it, and be as much of a devil in this heart as he is now. The Devil once seemed to be religious from fear of torment: Luke 8:28– “When he saw Jesus, he cried out and fell down before him, and with a loud voice said, What have I to do with thee, Jesus, thou Son of God most high? I beseech Thee, torment me not.” Here is external worship. The Devil is religious; he prays — he prays in a humble posture; he falls down before Christ, he lies prostrate; he prays earnestly, he cries with a loud voice; he uses humble expressions — “I beseech Thee, torment me not;” he uses respectful, honourable, adoring expressions — “Jesus, Thou Son of God most high.”Nothing was wanting but LOVE.

~ Jonathan Edwards,  Treatise on Grace