Proverbs 22:18 (BSB)

for it is pleasing when you keep them within you and they are constantly on your lips.

From Proverbs 22. Also in the ESV.

Commentary on Proverbs 22:18

• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on Proverbs 22:17-21: Solomon here changes his style and manner of speaking. Hitherto, for the most part, since the beginning of ch. 10, he had laid down doctrinal truths, and but now and then dropped a word of exhortation, leaving us to make the application as we went along; but here, to the end of ch.
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on Proverbs 22:18: For it is a pleasant thing if thou keep them within thee,.... Or, "in thy belly" (a). That is, in thine heart, in the inmost recesses of it; where the words or doctrines of the wise should be received in the love of them, and carefully laid up and retained; which will upon reflection yield much pleasure, like Ezekiel's roll, which was in his belly...
• Jamieson-Fausset-Brown (Reformed), Commentary Critical and Explanatory on the Whole Bible on Proverbs 22:18: These lessons must be laid up in the mind, and fitted--or better, "fixed" in the lips so as to be ever ready.