The word(s) "mature" appears 2 time(s) in 2 verse(s) in Quran in Saheeh International translation.

(1) Allah knows what every female carries and what the wombs lose [prematurely] or exceed. And everything with Him is by due measure.

(سورة الرعد, Ar-Ra'd, Chapter #13, Verse #8)
(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) And when he attained his full strength and was [mentally] mature, We bestowed upon him judgement and knowledge. And thus do We reward the doers of good.

(سورة القصص, Al-Qasas, Chapter #28, Verse #14)
(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)