EXOD495 The wicked receive only suffering of vengeance. But suffering as a test is only brought upon the righteous -- for they accept them with love and further improve their deeds, and the suffering they experience is for their own good [when they pass the test, their prestige and honor increase (see this verse, Rashi)], for their benefit [because they further improve their deeds, as Rabbeinu Yonah just said], and for enhancing their reward, as the pasuk says (Tehillim 11:5), "Hashem tests the righteous." Our Sages, z"l, used the following analogy and said (Bereishis Rabbah 32:3), "When the owner of the flax knows that his flax is strong, he beats it fully to make it soft and good."