Proverbs 15:21

Folly [is] joy to [him that is] destitute of wisdom: but a man of understanding walketh uprightly.

Ver. 21. Folly is joy to him that is destitute of understanding.] See Trapp on " Pro 10:23 "

But a man of understanding walketh uprightly.] And he doth it with delight, as the opposition implies. Christ's "burden" is no more "grievous" to him than the wing is to the bird. Mat 11:30 1Jn 5:3 His sincerity supplies him with serenity; a the joy of the Lord, as an oil of gladness, makes him lithe and nimble in ways of holiness. And this spiritual joy, in some, is a habitual gladness of heart, which constantly, after assurance, is found in them, though they feel not the passions of joy; but in others there are felt at some times the vehement passions of joy, but not any constant gladness.

a Sinceritas serenitatis mater, sine qua tranquillitas omnis tempestas est. - Isidor.