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

(1) And remember We took a covenant from the Children of Israel (to this effect): Worship none but Allah; treat with kindness your parents and kindred, and orphans and those in need; speak fair to the people; be steadfast in prayer; and practise regular charity. Then did ye turn back, except a few among you, and ye backslide (even now).

(سورة البقرة, Al-Baqara, Chapter #2, Verse #83)
(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) If ye backslide after the clear (Signs) have come to you, then know that Allah is Exalted in Power, Wise.

(سورة البقرة, Al-Baqara, Chapter #2, Verse #209)
(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)