Charles H. Spurgeon on Psalms 78:37

For their heart was not right with him. There was no depth in their repentance, it was not heart work. They were fickle as a weathercock, every wind turned them, their mind was not settled upon God. Neither were they stedfast in his covenant. Their promises were no sooner made than broken, as if only made in mockery. Good resolutions called at their hearts as men do at inns; they tarried awhile, and then took their leave. They were hot today for holiness, but cold towards it tomorrow. Variable as the hues of the dolphin, they changed from reverence to rebellion, from thankfulness to murmuring. One day they gave their gold to build a tabernacle for Jehovah, and the next they plucked off their earrings to make a golden calf. Surely the heart is a chameleon. Proteus had not so many changes. As in the ague we both burn and freeze, so do inconstant natures in their religion.