( فَإِذَا جَاءَتْهُمُ الْحَسَنَةُ ) (But when good came to them): (Good) here refers to the source from any good thing.

( وَإِن تُصِبْهُمْ سَيِّئَةٌ يَطَّيَّرُوا بِمُوسَىٰ وَمَن مَّعَهُ ) (And if a bad [condition] struck them, they saw an evil omen in Moses and those with him): The Arabic word of (evil omen) derived from the Arabic root word (bird). In ancient time when a person wanted to know what course of action to take in something, he would release a bird. If the bird flew to the right, it was considered a good omen, and if it flew to the left, it was as a bad omen.

Thus, they claimed that any goodness that had befallen them was due to their own efforts, as mentioned in the story of Qarun:

 إِنَّمَا أُوتِيتُهُ عَلَىٰ عِلْمٍ عِندِي

(I was only given it because of knowledge I have) (Al-Qasas: 78)

Qarun attributed his success to his own knowledge, strength, wealth, and courage, forgetting Allah (swt).

Hence, whenever they faced an affliction, they became pessimistic and blamed Prophet Moses (PBUH), claiming that he (PBUH) was the cause behind all of their misfortune.

( أَلَا إِنَّمَا طَائِرُهُمْ عِندَ اللَّهِ) (Unquestionably, their fortune is with Allah): Their misfortune was from Allah (swt) due to their disbelief and injustice. That is why these punishments, such as drought, famine, decreased fruitfulness, and other trials, were afflicted upon them by Allah (swt).

As mentioned before, Allah (swt) orders human beings to have certain initiatives in order to achieve specific matters. At the same time, there are other matters that are beyond human influence and are decreed by Allah (swt). For example, if you told your child to study, but he did not, then as a result, he failed. In this case, it cannot be said that it was a bad omen or that he suffered an envious evil eye which caused him to fail. In fact, this was because he did not fulfil his duty of studying. On the other hand,  if the child was intelligent and he studied hard, but he fell ill before going to the exam or some other matter befalls him which is beyond his control, we should say: ‘It was all decreed by Allah’.

( وَلَٰكِنَّ أَكْثَرَهُمْ لَا يَعْلَمُونَ ) (but most of them do not know): In fact,  many do not realize that humans are held accountable according to their ability which was determined by Allah (swt). Allah (swt) has linked outcomes to the means and actions taken.