C. F. Keil and Franz Delitzsch on Proverbs 19:20

Pro 19:20 20 Hearken to counsel, and receive instruction,      That thou mayest become wise afterwards.

The rule of morals, Pro 12:15, receives here the paraenetic tone which is the keynote of the introduction chap. 1-9. Löwenstein translates: that thou mayest finally become wise. But בּאחריתך corresponds rather to our “hinfort” [posthac] than to “endlich” [finally]. He to whom the warning is directed must break with the self-willed, undisciplined ראשׁית beginning of his life, and for the future (τὸν ἐπίλοιπον ἐν σαρκὶ χρόνον, 1Pe 4:2) become wise. The relative contrast between the two periods of life is the same as at Job 8:7.