What is the meaning of verse 9 in Surah Az-Zumar?

Ibn Kathir mentioned that the verse "Is one who is devoutly obedient during the hours of the night..." was revealed concerning the believer who is obedient to Allah and His Messenger, who fears the Hereafter and hopes for his Lord's mercy in his worship, being both fearful and hopeful. He interpreted "qanit" (devoutly obedient) as obedience to Allah and His Messenger, and "ana' al-layl" (hours of the night) as all its times. He also reported from Ibn Omar that it was revealed about Uthman ibn Affan due to his abundant prayer and night vigil, even though the verse is general for every devoutly obedient person. He concluded that the noble verse "Say, 'Are those who know equal to those who do not know?'" establishes that the devoutly obedient worshipping believer is not equal to the polytheist, and that people of understanding are those who recognize this difference.