The word(s) "flag" appears 3 time(s) in 3 verse(s) in Quran in Abdullah Yusuf Ali translation.

(1) But if any one earns a fault or a sin and throws it on to one that is innocent, He carries (on himself) (Both) a falsehood and a flagrant sin.

(سورة النساء, An-Nisaa, Chapter #4, Verse #112)
(Arabic, Transliteration, Urdu (Ahmed Ali), Urdu (Jalandhry), Farsi, Yusuf Ali, Shakir, Picthal, Mohsin Khan, French, Spanish, Indonesian, Malay, German, Bosnian, Russian, Dutch, Italian, Portuguese, Tafsir - Jalal ad-Din, Tafsir - King Fahad Quran Complex)

(2) They celebrate His praises night and day, nor do they ever flag or intermit.

(سورة الأنبياء, Al-Anbiyaa, Chapter #21, Verse #20)
(Arabic, Transliteration, Urdu (Ahmed Ali), Urdu (Jalandhry), Farsi, Yusuf Ali, Shakir, Picthal, Mohsin Khan, French, Spanish, Indonesian, Malay, German, Bosnian, Russian, Dutch, Italian, Portuguese, Tafsir - Jalal ad-Din, Tafsir - King Fahad Quran Complex)

(3) But is the (Unbelievers) are arrogant, (no matter): for in the presence of thy Lord are those who celebrate His praises by night and by day. And they never flag (nor feel themselves above it).

(سورة فصلت, Fussilat, Chapter #41, Verse #38)
(Arabic, Transliteration, Urdu (Ahmed Ali), Urdu (Jalandhry), Farsi, Yusuf Ali, Shakir, Picthal, Mohsin Khan, French, Spanish, Indonesian, Malay, German, Bosnian, Russian, Dutch, Italian, Portuguese, Tafsir - Jalal ad-Din, Tafsir - King Fahad Quran Complex)