'A'isha (Allah be pleased with her) reported that Messenger of Allah ﷺ used to exert himself in devotion during the last ten nights to a greater extent than at any other time. (Using translation from Muslim 1175)
عَائِشَةُ كَانَ رَسُولُ اللهِ ﷺ «يَجْتَهِدُ فِي الْعَشْرِ مَا لَا يَجْتَهِدُ فِي غَيْرِهَا»