The Messenger of Allah (may Allah's peace and blessings be upon him) would strive more in Ramadan than he would strive in other than it, and in the last ten of it than he would strive in other than them. [Muslim]

"كان رسول الله -صلى الله عليه وسلم- يَجْتَهِدُ في رمضان ما لا يَجْتَهِدُ في غيره، وفي العَشْرِ الأوَاخِرِ منه ما لا يَجْتَهِدُ في غيره. [صحيح.] - [رواه مسلم.]"