The example of what they spend in this worldly life is like that of a wind containing frost which strikes the harvest of a people who have wronged themselves [i.e., sinned] and destroys it. And Allāh has not wronged them, but they wrong themselves.
The example of what disbelievers spend in charity, and what they expect to receive of rewards, is like a wind which is extremely cold that hits the crops of a people who wronged themselves by not doing as they were instructed, ruining their crops when they had expected to have a good harvest. Disbelief also ruins the rewards of good deeds. Allah does not wrong them for He is far above any injustice, rather, they wrong themselves through their disbelief in Allah and His prophets.