Narrated Anas bin Malik (r), Ummur Rubay bint al-Bara (the mother of Haritha bin Suraqa) came to the Prophet (saw) and said, “O Allah’s Prophet! Will you tell me about Haritha? Haritha has been killed (ie Shaheed) on the day of Badr with an arrow fired by an unidentified person.” She added, “If he is in Paradise I will be patient, otherwise I will weep bitterly for him.” He said, “O mother of Haritha! There are gardens in Paradise and your son got Firdaus al-‘Ala (ie the best place of Paradise).” (Sahih Bukhari, p.394, vol.1)
This is the special aspect of Jihaad, that however the death occurs, the Muslim is granted the high grades of Jannah.In the battle of Khaybar, a Sahabi was Shaheed by his own sword by accident. When the people started gossiping about this incident the Prophet (saw) said he will be given double reward than the normal Shuhadah, one reward for Shahadah and the second reward due to the people gossipping about him.
It has been stated in another narration that whoever set out for Jihad and is killed by falling from his mount or from the bite of a poisonous insect or for any other reason, he will enter Paradise.
JANNAH FIRDAUS BY SIYAD MAHAMAD