Sahih al-Bukhari 36
صحيح البخاري#36SahihNarrated Abu Huraira: The Prophet (ﷺ) said, "The person who participates in (Holy battles) in Allah's cause and nothing compels him to do so except belief in Allah and His Apostles, will be recompensed by Allah either with a reward, or booty (if he survives) or will be admitted to Paradise (if he is killed in the battle as a martyr). Had I not found it difficult for my followers, then I would not remain behind any sariya going for Jihad and I would have loved to be martyred in Allah's cause and then made alive, and then martyred and then made alive, and then again martyred in His cause
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 2:29