the Prophet said: "There are no days more beloved to Allah that He be worshipped in them than the ten days of Dhul-Hijjah, fasting every day of them is the equivalent of fasting a year, and standing every night of them (in prayer) is the equivalent of standing on the Night of Qadr."
عَنِ النَّبِيِّ ﷺ قَالَ مَا مِنْ أَيَّامٍ أَحَبُّ إِلَى اللَّهِ أَنْ يُتَعَبَّدَ لَهُ فِيهَا مِنْ عَشْرِ ذِي الْحِجَّةِ يَعْدِلُ صِيَامُ كُلِّ يَوْمٍ مِنْهَا بِصِيَامِ سَنَةٍ وَقِيَامُ كُلِّ لَيْلَةٍ مِنْهَا بِقِيَامِ لَيْلَةِ الْقَدْرِ