The word(s) "unfailing" appears 4 time(s) in 4 verse(s) in Quran in Muhammad Pickthal translation.

(1) And as for those who will be glad (that day) they will be in the Garden, abiding there so long as the heavens and the earth endure save for that which thy Lord willeth: a gift unfailing.

(سورة هود, Hud, Chapter #11, Verse #108)
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(2) And lo! thine verily will be a reward unfailing.

(سورة القلم, Al-Qalam, Chapter #68, Verse #3)
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(3) Save those who believe and do good works, for theirs is a reward unfailing.

(سورة الإنشقاق, Al-Inshiqaaq, Chapter #84, Verse #25)
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(4) Save those who believe and do good works, and theirs is a reward unfailing.

(سورة التين, At-Tin, Chapter #95, Verse #6)
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