וְֽחַנְפֵי־לֵ֭ב יָשִׂ֣ימוּ אָ֑ף לֹ֥א יְ֝שַׁוְּע֗וּ כִּ֣י אֲסָרָֽם׃
Rashi on Job
But the wicked of heart who are wicked—they bring about wrath; when suffering comes upon them, they curse and blaspheme,
Malbim on Job
The insincerity of those who are not truly righteous might not show up during times of fortune; when they are well off they can afford the luxury of virtue. But as soon as misfortune strikes them, their hypocrisy comes to light.