Surah 7. Al-A'raf, Ayah 131

The phrase tatayyara bihi signifies "he attributed an evil omen to him" or "he augured evil from him". It is based on the pre-Islamic Arab custom of divining the future or establishing an omen from the flight of birds. Thus, the noun ta'ir (lit., "a flying creature" or "a bird") is often used in classical Arabic to denote "destiny" or "fortune", both good and evil, as in the next sentence of the above verse ("their [evil] fortune had been decreed by [lit., "was with"] God"). Instances of this tropical employment of the expressions ta'ir and tayr and their verbal derivations are also found in 3:49 , 5:110 , 17:13 , 27:47 , {36:18-19}.

 In psychology, this is called self-serving bias and scapegoating.

Their superstition ascribed the punishment of their own wickedness to some evil omen. They thought Moses and his people brought them ill-luck. They did not look within themselves to see the root of evil, and the cause of their punishment! So it happens in all ages. People blame the righteous for something which they do, different from other men, instead of searching out their own lapses from rectitude, which are punished by Allah.