Abu Dharr (May Allah be pleased with him) reported:
The Messenger of Allah (ﷺ) was asked: "Which deed is the best?" He (ﷺ) replied, "Faith in Allah and Jihad (fighting, struggle) in the Cause of Allah."[Al-Bukhari and Muslim].
App reference: Book 12, Hadith 3
Arabic/English book reference: Book 12, Hadith 1287