Though he spare it, and forsake it not; but keep it still within his mouth:

King James Translators' Notes

within...: Heb. in the midst of his palate

Matthew Henry's Concise Commentary

20:10-22 The miserable condition of the wicked man in this world is fully set forth. The lusts of the flesh are here called the sins of his youth. His hiding it and keeping it under his tongue, denotes concealment of his beloved lust, and delight therein. But He who knows what is in the heart, knows what is under the tongue, and will discover it. The love of the world, and of the wealth of it, also is wickedness, and man sets his heart upon these. Also violence and injustice, these sins bring God's judgments upon nations and families. Observe the punishment of the wicked man for these things. Sin is turned into gall, than which nothing is more bitter; it will prove to him poison; so will all unlawful gains be. In his fulness he shall be in straits, through the anxieties of his own mind. To be led by the sanctifying grace of God to restore what was unjustly gotten, as Zaccheus was, is a great mercy. But to be forced to restore by the horrors of a despairing conscience, as Judas was, has no benefit and comfort attending it.