Ibn ‘Umar reported God’s Messenger as saying, “Prayer during the night should consist of pairs of <i>rak'as</i>, but if one of you fears the morning is near he should pray one <i>rak'a</i> which will make his prayer an odd number for him.” (Bukhari and Muslim.)

عَنِ ابْنِ عُمَرَ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «صَلَاةُ اللَّيْلِ مَثْنَى مَثْنَى فَإِذَا خَشِيَ أَحَدُكُمُ الصُّبْحَ صَلَّى رَكْعَةً وَاحِدَة توتر لَهُ مَا قد صلى»