Albert Barnes Commentary Psalms 106:15

"And he gave them their request, But sent leanness into their soul." — Psalms 106:15 (ASV)

And he gave them their request - By sending great quantities of quails (Numbers 11:31–32).

But sent leanness into their soul - The word translated “leanness” comes from a verb, רזה râzeh, which means to make thin, to cause to waste away, or to destroy. The root idea is that of abrading or “scraping;” and hence, it means to become lean or to waste away. It occurs only here, in Isaiah 10:16 (where it is rendered “leanness”), and in Micah 6:10 (where it is rendered “scant,” with a marginal reading of “leanness”). This means that the effect of these circumstances on their souls was similar to the effect on the body when it wastes away from disease or lack of food.

This effect often occurs. In the gratification of their desires, and in great temporal success and prosperity, individuals, churches, and nations often forget their dependence on God; lose their sense of the value of spiritual privileges and blessings; become satisfied with their condition; grow self-confident and proud; and forfeit the favor of God.

If we pray for temporal prosperity, we should also pray for grace commensurate with it, so that it may be a blessing and not a curse. Similarly, if prosperity comes to us when it has not been a direct object of our prayer—if we inherit riches, if our plans are successful beyond our expectations, or, in the language of the world, if “fortune smiles upon us”—we should offer special prayer that it may not be a curse rather than a blessing. We should pray that it may be received and used in such a way as not to alienate our minds from God.

Few Christian people can bear continued success in life; few are those who are not injured by it. It is rare that growth in grace keeps pace with uninterrupted worldly prosperity; it is rare that earthly blessings are received and used in such a way that they are seen as a means of grace and not a hindrance to growth in piety. A person does not know what is best for them when their heart is set on worldly prosperity, and God is more benevolent to people than they are to themselves in withholding what is so often the object of their intense desire.

“What is asked in passion, is often given in wrath.” — Henry