This excerpt is taken from the book of Sheikh Abi Abdul Saboor Abdul Ghafoor Damni Fazail al-Jihad.
عن سلمان قال سمعت رسول الله يقول رباط يوم وليلة خير من صيام شهر وقيامه وإن مات جرى عليه عمله الذى كان يعمله وأجري عليه رزقه وأمن الفتان.
Narrated Salman al-Farsi, may Allah be pleased with him, that I heard the Messenger of Allah, peace and blessings be upon him, say: "One day and one night of guarding the border (shared with the enemy) is better than fasting for a month and standing in prayer for a month, and if he dies, then the deeds he used to do will continue for him. His provision will continue, and he will be protected from the trials of the grave."
Reference: (Sahih Muslim) (Narrated by Muslim, Book of Leadership, Chapter on the Virtue of Vigilance in the Cause of Allah, Number: 1913)
Explanation
This hadith mentions the further virtue of ribat, meaning ribat is such an act that a person who performs it for just one day or one night accumulates more rewards than fasting for a month and praying at night for a month. If death occurs while on guard, the chain of reward and recompense continues, and according to the Quran, عند ربهم یرزقون, they are provided sustenance together in the Barzakh realm, and they are also saved from the trials of the grave after death.
Note: Here, أمن الفتان refers to the trial of the grave because in Sunan Abi Dawood, Book of Jihad,
Reference: Chapter on the Virtue of Ribat, Number: 2500
, in the hadith of Fudalah bin Ubaid (may Allah be pleased with him), the words ويؤمن من فتان القبر appear, which clearly indicate that أمن الفتان refers to the trial of the grave, as we mentioned above.