Waayyooba ith nada rabbahu annee massaniya addurru waanta arhamu arrahimeen (surah Anbiya: 83)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(21:83) And We had given Job *76 the same (blessing of wisdom and knowledge). Remember when he invoked his Lord, saying, "I have been afflicted with the disease, and Thou art most Merciful. " *77

Wa Ayyooba iz naadaa Rabbahooo annee massaniyad durru wa Anta arhamur raahimeen

*76) There is a wide divergence of opinion concerning the personality, period and nationality of Prophet Job. Some commentators opine that he was an Israelite, while others think that he was an Egyptian or an Arab who lived before Prophet Moses, or during the time of Prophets David and Solomon. As all these conjectures are based on the Book of Job, which is self-contradictory and against the Qur'an, nothing can be said about him with certainty, but in the light of the Book of lsaiah (8th century BC) and the Book of Ezekiel (6th century BC), which are more trustworthy works, he lived in the 9th century BC or even earlier. As regards his nationality, the context in which his name occurs in IV: 163 and VI: 84, it may be assumed that he was an Israelite. According to a saying of Hadrat Wahb bin Munabbih, he might have been from the offspring of Esau, a son of Prophet lsaac.
*77) The words of the prayer are note-worthy. Prophet Job mentions his distress but. does not say anything more to his Lord except: "Thou art most Merciful" This is a great proof of his fortitude, noble and contented nature.