كتاب الجهاد
Read the English translation first, with the original Arabic directly underneath.
Narrated Fadalah ibn Ubayd:
The Prophet (ﷺ) said: Everyone who dies will have fully complete his action, except one who is on the frontier (in Allah's path), for his deeds will be made to go on increasing till the Day of Resurrection, and he will be safe from the trial in the grave.
كُلُّ الْمَيِّتِ يُخْتَمُ عَلَى عَمَلِهِ، إِلاَّ الْمُرَابِطَ فَإِنَّهُ يَنْمُو لَهُ عَمَلُهُ إِلَى يَوْمِ الْقِيَامَةِ وَيُؤَمَّنُ مِنْ فَتَّانِ الْقَبْرِ