The word(s) "constancy" appears 2 time(s) in 2 verse(s) in Quran in Muhammad Pickthal translation.

(1) And verily We made a covenant of old with Adam, but he forgot, and We found no constancy in him.

(سورة طه, Taa-Haa, Chapter #20, Verse #115)
(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) Men whom neither merchandise nor sale beguileth from remembrance of Allah and constancy in prayer and paying to the poor their due; who fear a day when hearts and eyeballs will be overturned;

(سورة النور, An-Noor, Chapter #24, Verse #37)
(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)