"It was said, 'O Messenger of Allah, what equals Jihad?' He said: 'Verily, you (people) are not capable of it.' So they repeated it to him two or three times, each time he said, 'You (people) are not capable of it.' Then he said the third time: 'The example of the Mujahid in the path of Allah is like the one who fasts and stands (in prayer) and does not slacken from Salat, nor fasting, until the Mujahid in the cause of Allah returns.'" There are narrations on this topic from Ash-Shifa', 'Abdullah bin Hubshi, Abu Musa', Abu Sa'eed, Umm Malik Al-Bahziyyah, and Anas. This Hadith is a Hasan Sahih. And it has been reported through more than one route from Abu Hurairah from the Prophet ﷺ.  

قِيلَ يَا رَسُولَ اللَّهِ مَا يَعْدِلُ الْجِهَادَ قَالَ لاَ تَسْتَطِيعُونَهُ فَرَدُّوا عَلَيْهِ مَرَّتَيْنِ أَوْ ثَلاَثًا كُلُّ ذَلِكَ يَقُولُ لاَ تَسْتَطِيعُونَهُ فَقَالَ فِي الثَّالِثَةِ مَثَلُ الْمُجَاهِدِ فِي سَبِيلِ اللَّهِ مَثَلُ الْقَائِمِ الصَّائِمِ الَّذِي لاَ يَفْتُرُ مِنْ صَلاَةٍ وَلاَ صِيَامٍ حَتَّى يَرْجِعَ الْمُجَاهِدُ فِي سَبِيلِ اللَّهِ  

"The Messenger of Allah ﷺ said: meaning: Allah Mighty and Sublime is He says: 'The Mujahid in My cause, he has guarantee fro Me. If I I seize him, I cause him to inherit Paradise, and if I return him, I return him with a reward or spoils of war.'" [He said:] This Hadith is Gharib Sahih from this route.  

قَالَ رَسُولُ اللَّهِ ﷺ يَعْنِي يَقُولُ اللَّهُ ﷻ الْمُجَاهِدُ فِي سَبِيلِ اللَّهِ هُوَ عَلَىَّ ضَامِنٌ إِنْ قَبَضْتُهُ أَوْرَثْتُهُ الْجَنَّةَ وَإِنْ رَجَعْتُهُ رَجَعْتُهُ بِأَجْرٍ أَوْ غَنِيمَةٍ قَالَ هُوَ صَحِيحٌ غَرِيبٌ مِنْ هَذَا الْوَجْهِ