He supported his people to suffice their needs and administered justice among them. That is why he was called Dhul - Kifl. Dhul - Kifl literally means "possessor of, or giving, a double requital or portion."
Immediately following Ayyub's (peace be upon Him) story in the Qur'an, Almighty Allah (Glory be to Him) also directed: "Remember Our slaves, Ibrahim, Isaaq and Yaqub (all) owners of strength (in worshipping Us) and also of religious understanding. Verily, We did choose them by granting them (a good thing ) the remembrance of the home (in the Hereafter and they used to make the people remember it and also they used to invite the people to obey Allah and to do good deeds for the Hereafter). And they are in Our Sight, verily of the chosen and the best! Remember Ismael, Al-Yasaa and Dhul Kifl all are among the best." Qur’an.Surah Saad 38:45-48
Stories of the Prophets by Ibn Kathir