This oracle of Yahweh, via Isaiah, centers on insincere worship. They adore the Lord with their mouths and lips, but their hearts are far away. They only praise the Lord because of human demands, as they recite rote prayers. However, Yahweh, the Lord, was going to do marvelous, amazing, and shocking things for his people. The wisdom of the wise would perish, while the discernment of the discerning was hidden.
Sirach points out that just as your taste buds can tell the difference between various kinds of food, so too the mind should be able to discern the difference between true and false words. Both the stomach and the mind can absorb all kinds of foods and words. However, just as one food is better for you than another, so too the perverse mind can cause grief. The experienced person will be able to verbally payback the false words and the perverse minds.