Mishkat al-Masabih 7 Fasting كتاب الصوم 127

وَعَنِ ابْنِ عَبَّاسٍ أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: الْتَمِسُوهَا فِي الْعَشْرِ الْأَوَاخِرِ مِنْ رَمَضَانَ لَيْلَةَ الْقَدْرِ: فِي تَاسِعَةٍ تَبْقَى فِي سَابِعَةٍ تَبْقَى فِي خَامِسَةٍ تَبْقَى. رَوَاهُ البُخَارِيّ

Ibn ‘Abbas reported the Prophet as saying, “Seek lailat al-qadr in the last ten nights of Ramadan, on the twenty-first, twenty-third and twenty-fifth.” Bukhari transmitted it.