"OPEN WIDE YOUR MOUTH and I will fill it" (Ps. 81:10): the symbolism is transparent.
God is perfectly willing and able to satisfy all our deepest needs and longings. Implicitly, the problem is that we will not even open our mouths to enjoy the food he provides. The symbolism returns in the last verse: while the wicked will face punishment that lasts forever, "you would be fed with the finest of wheat; with honey from the rock I would satisfy you" (Ps. 81:16).
Of course, God is talking about more than physical food (though scarcely less). The setting is a common one both in the Psalms and in the narrative parts of the Pentateuch. God graciously and spectacularly rescued the people from their slavery in Egypt, responding to their own cries of distress. "I removed the burden from their shoulders,"God says. "In your distress you called and I rescued you" (Ps. 81:6-7). Then comes the passage that leads to the line quoted at the beginning of this meditation:
Hear, O my people, and I will warn you –
if you would but listen to me, O Israel!
You shall have no foreign god among you;
you shall not bow down to an alien god.
I am the LORD your God, who brought you up out of Egypt.
Open wide your mouth and I will fill it (Ps. 81:8-10).
Historically, of course, the response of the people was disappointing: "my people would not listen to me; Israel would not submit to me" (Ps. 81:11). In that case, they were not promised the satisfaction symbolized by full mouths. Far from it, God says, "So I gave them over to their stubborn hearts to follow their own devices" (Ps. 81:12).
Of course, the nature of the idolatry changes from age to age. I recently read some lines from John Piper:
The greatest enemy of hunger for God is not poison but apple pie. It is not the banquet of the wicked that dulls our appetite for heaven, but endless nibbling at the table of the world. It is not the X-rated video, but the prime-time dribble of triviality we drink in every night. For all the ill that Satan can do, when God describes what keeps us from the banquet table of his love, it is a piece of land, a yoke of oxen, and a wife (Luke 14:18-20). The greatest adversary of love to God is not his enemies but his gifts. And the most deadly appetites are not for the poison of evil, but for the simple pleasures of earth. For when these replace an appetite for God himself, the idolatry is scarcely recognizable, and almost incurable (A Hunger for God, Wheaton: Crossway, 1997, 14).
"Open wide your mouth and I will fill it."
Deuteronomy 1; Psalms 81-82; Isaiah 29; 3 John