(26) باب الدُّعَاءِ فِي صَلاَةِ اللَّيْلِ وَقِيَامِهِ
Abu Huraira reported Allah's Apostle (ﷺ) as saying When any one of you gets up at night, he should begin the prayer with two short rak'ahs.
Reference: Sahih Muslim 768
In-book reference: Book 6, Hadith 235
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1690