Yazid bin Harun يزيد بن هارون · The Book on Virtues of Jihad

That the Messenger of Allah (ﷺ) said: "The deeds of everyone who dies are sealed. Except for the one who dies guarding the frontier from the enemy, in the cause of Allah. For indeed his actions are increased for him until the Day of Judgement, and he is secure from the tribulation of the grave." And I heard the Messenger of Allah (ﷺ) saying: "The Mujahid is one who strives against his own soul." There are narrations on this topic…

That the Prophet (ﷺ) said similarly.

"The Messenger of Allah (ﷺ) was asked about a man who fights out of bravery, one who fights out of protection (for himself or others), and one who fought to be seen. Which of them is in the cause of Allah ? He said: 'Whoever fought so that the Word of Allah is supreme, then he is in Allah's cause.'" There is something on this topic from 'Umar. This Hadith is Hasan Sahih.