The word(s) "frighten" appears 2 time(s) in 2 verse(s) in Quran in Abdullah Yusuf Ali translation.

(1) Men said to them: "A great army is gathering against you": And frightened them: But it (only) increased their Faith: They said: "For us Allah sufficeth, and He is the best disposer of affairs."

(سورة آل عمران, Aal-i-Imraan, Chapter #3, Verse #173)
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(2) Is not Allah enough for his Servant? But they try to frighten thee with other (gods) besides Him! for such as Allah leaves to stray, there can be no guide.

(سورة الزمر, Az-Zumar, Chapter #39, Verse #36)
(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)