In hardships and calamities, people show their true nature

Al-Hasan al-Basri said: “As long as people are in prosperity, their position is hidden. But as soon as troubles befall them, they immediately show their nature, and the believer shows his faith, and the hypocrite – his hypocrisy .
al-Bayhaqi in Shu’ab al-iman (12/387).

Abu Sa’id al-Kharraz said: “Indeed, prosperity hides the nature of the righteous and the wicked, but when misfortunes befall, true men begin to show themselves.”
Ibn al-Jawzi in al-Muntazim (11/282).

Sheikhul-Islam Ibn Taymiyyah said: “ What is hidden in the hearts is revealed during trials . ”
See Majmu’ul-fataawa (9/20).