In Parshat Chukat, we read about the encounter with the king of Arad. In the beginning of פרק כ"א it says, "וישמע הכנעני מלך ערד ישב הנגב כי בא ישראל דרך האתרים", “The King of Arad, who lived in the South, heard that Israel came by way of Atarim.” Immediately following this, the king of Arad goes to fight against בני ישראל. Many commentators ask what the king of Arad heard which prompted him to attack בני ישראל. After all, we know that the nations of the world were very fearful of בני ישראל. In ספר יהושע, רחב says to the spies that when the inhabitants of ארץ כנען learned about that which Hashem did for בני ישראל, ונשמע וימס לבבנו"," “We heard and our hearts melted.” Clearly, the nations would not attack בני ישראל because of their fear of being destroyed by Hashem. Why, then, did the king of Arad attack בני ישראל?
Ramban quotes אונקלוס and explains that when the מרגלים were returning to report to בני ישראל, the king of Arad saw them and decided to attack. He says that "האתרים" is related to the word תרים, “spies.” However, this does not explain why the king of Arad decided to provoke בני ישראל. Nechama Lebowitz explains that when בני ישראל sent the מרגלים, it was a sign of their fear and lack of faith in Hashem. The king of Arad decided to capitalize on this fear and attacked them when they were vulnerable.
The lesson from this short episode is very important. When בני ישראל lost faith in Hashem, they were immediately attacked. If we have אמונה in Hashem, He will protect us from any troubles that befall us.