Psalms 106:15

Sent leanness - They despised the manna, and called it light, that is, innutritive, bread. God gave flesh as they desired, but gave no blessing with it; and in consequence they did not fatten, but grew lean upon it. Their souls also suffered want.

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" is from a verb - רזה râzeh - to make thin; to cause to waste away; to destroy. The radical idea is that of abrading or "scraping;" and hence, it means to become lean, to waste away. It occurs only here and in Isaiah 10:16, rendered "leanness," and in Micah 6:10, rendered "scant;" margin, "leanness." It means here that the effect of all this on their souls was similar to the effect on the body when it wastes away by disease or want of food. This effect often occurs. In the gratification of their desires, in great temporal success and prosperity, individuals, churches, nations, often forget their dependence on God; lose their sense of the value of spiritual privileges and blessings: are satisfied with their condition; become selfconfident and proud, and forfeit the favor of God. If we pray for temporal prosperity, we should also pray that we may at the same time have grace commensurate with it, that it may be a blessing and not a curse; if we are visited with prosperity when it has not been a direct object of our prayer - if we inherit riches, or if our plans are successful beyond our expectations - or, in the language of the world, if "fortune smiles upon us," there should be special prayer on our part that it may not be a curse rather than a blessing; that it may be so received and used as not to alienate our minds from God. Few are the Christian people who can bear continued success in life; few are those who are not injured by it; rare is it that growth in grace keeps pace with uninterrupted worldly prosperity; rare is it that the blessings of earth are so received and employed that they are seen to be a means of grace, and not a hindrance to growth in piety. A man does not know what is best for him when his 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.

106:15 Souls - Into their bodies. So their inordinate desire of pampering their bodies, was the occasion of destroying them.