The Letter Qaf 50:40. Juz 26, page 520.
وَمِنَ ٱلَّيْلِ فَسَبِّحْهُ وَأَدْبَـٰرَ ٱلسُّجُودِ٤٠
And in the night-time hymn His praise, and after the (prescribed) prostrations.
Qaf 50:40, translated by Marmaduke Pickthall