The Messenger of Allah ﷺ used to exert himself in worship during the last ten nights in a way that he did not at any other time.
كان رسول الله ﷺ يجتهد في العشر الأواخر ما لا يجتهد في غيره.
Muslim narrated it in itikaf (1175) via Abdul-Wahid bin Ziyad, from Hasan bin Ubaydullah, who said, "I heard Ibrahim say, 'I heard Aswad bin Yazid say, "Ayesha said,"'" and he mentioned it.