In this chapter the reality of the "word made flesh" meaning "word made manna" is brought forth. This application is made practical from the common theme of "tasting" the word of God.
Dr Leithart conclusion is then fairly simple. Enjoy tasting good things and you won't be able to stand a filthy mouth. The consumption of the word and Scriptures controls the tongue. It is sanctification.
The application of this to the Lord's Supper is less straight forward. Christ body truly is best reflected as the manna poured out for His people. He then truly is our "daily bread". But the people were driven to complain because of their dissatisfaction with the bread. They wanted to taste something else.
So it is with the church, when our hearts are right the bread becomes sweeter then honey. We can taste and see that The Lord is good. But for many with corrupt hearts the bread only drives them back to Egypt.
