"The Messenger of Allah would struggle (to perform Salat more) during the last ten (nights) more than he would struggle in the rest of it." (Using translation from Tirmidhī 796)
كَانَ رَسُولُ اللهِ ﷺ يَجْتَهِدُ فِي الْعَشْرِ الْأَوَاخِرِ مَا لَا يَجْتَهِدُ فِي غَيْرِهِ