Charles H. Spurgeon on Psalms 78:36

Nevertheless they did flatter him with their mouth. Bad were they at their best. False on their knees, liars in their prayers. Mouth worship must be very detestable to God when dissociated from the heart: other kings love flattery, but the King of kings abhors it. Since the sharpest afflictions only extort from carnal men a feigned submission to God, there is proof positive that the heart is desperately set on mischief, and that sin is ingrained in our very nature. If you beat a tiger with many stripes you cannot turn him into a sheep. The devil cannot be whipped out of human nature, though another devil, namely, hypocrisy may be whipped into it. Piety produced by the damps of sorrow and the heats of terror is of mushroom growth; it is rapid in its springing up —"they enquired early after God" —but it is a mere unsubstantial fungus of unabiding excitement. And they lied unto him with their tongues. Their godly speech was cant, their praise mere wind, their prayer a fraud. Their skin deep repentance was a film too thin to conceal the deadly wound of sin. This teaches us to place small reliance upon professions of repentance made by dying men, or upon such even when the basis is evidently slavish fear, and nothing more. Any thief will whine out repentance if he thinks the judge will thereby be moved to let him go scot free.