Proverbs 18:20 New English Translation

²⁰From the fruit of a person’s mouth^[a] his stomach^[b] will be satisfied,^[c]
with the product of his lips he will be satisfied.

Proverbs 18:20 sn Two harvest images, fruit (from trees) and produce (from field crops), are applied to speech, represented by the mouth and lips. The “mouth” and the “lips” are metonymies of cause, with both lines indicating that speech is productive. The following verse about harvest of the tongue may be part of this proverb.
Proverbs 18:20 tn The noun בֶּטֶן (beten) can refer to the stomach, womb, or internal organs. In Prov 20:30 and 22:18 it appears to be metaphorical for the inner person, or soul. Given the references to the mouth, lips, and being satisfied, on one level it refers to the stomach. But it probably functions on a spiritual level as well, especially when read with the following verse.
Proverbs 18:20 tn Or “is satisfied.” The translation understands שָׂבַע (savaʿ) as stative “to be satisfied; be filled” rather than fientive, “to satisfy oneself,” so that the imperfect form is future. An imperfect verb may be future for both stative and dynamic verbs, and may be present for dynamic verbs. It is not possible to tell by morphological criteria whether the verb שָׂבַע is stative or dynamic, but elsewhere it behaves similarly to a stative.

New English Translation (NET)