John Calvin Commentary Psalms 78:18

"And they tempted God in their heart By asking food according to their desire." — Psalms 78:18 (ASV)

And they tempted God in their heart. This is the provocation mentioned in the preceding verse. It was not unlawful for them simply to ask for food when compelled to do so by the cravings of hunger. Who can blame people when, being hungry, they implore God to supply their needs?

The sin the Israelites were guilty of consisted in this: not content with the food He had appointed for them, they gave free rein to their lusts. At that time, He had begun to feed them with manna, as we will see again later. It was their loathing of that sustenance that impelled them eagerly to desire new food, as if they disdained the allowance assigned to them by their heavenly Father.

This is what is meant when it is said that they asked food for their soul. They were not forced to ask for it by hunger; instead, their lust was not satisfied with living on the provision God had appointed for them. For this reason, it is declared that they tempted God, exceeding, as they did, the limits He had set for them.

Whoever, undervaluing and despising the permission or freedom He grants, gives free rein to his own uncontrolled lust and desires more than is lawful, is said to tempt God. He acts as if he would make God submit to his own whim, or as if he questioned whether God could do more than He is pleased to actually do.

God has power to accomplish whatever He wills; and certainly, the person who would separate God's power from His will, or represent Him as unable to do what He wills, does all he can to tear Him apart. Those are guilty of this who are determined to test whether He will grant more than He has given them permission to ask.

Therefore, so that the lust of the flesh does not stir us up to tempt Him, let us learn to restrain our desires and humbly to be content within the limits prescribed for us. If the flesh is allowed to indulge itself without control, we will not be satisfied with ordinary bread but will often, and in many ways, murmur against God.