Good doctrine; not vain, or foolish, or false, or pernicious counsels, but such as are true and profitable. My law; God's law or commands, delivered to you by my mouth. See Poole on "Proverbs 3:1".
Related Commentaries of Proverbs 4:2
Proverbs 4:2
2 For I give you good doctrine, forsake ye not my law.