"Salman Al-Farisi passed by Shurahbil bin As-Simt while he was in garrison in which he and his companions were suffering from difficulties. He said to him: 'Shall I narrate to you - O Ibn As-Simt - a Hadith I heard from the Messenger of Allah (ﷺ) ?' He said: 'Of course.' He said: 'I heard the Messenger of Allah (ﷺ) saying: "(Ribat) Guarding the frontier for a day in the cause of Allah is more virtuous" - and perhaps he said: "better, than fasting a month and standing (in prayer) for it. And whoever dies in it, he is protected from the trials of the grave, and his deeds (continuously) multiplied until the Day of Resurrection. [Abu 'Eisa said:] This Hadith is Hasan.
حَدَّثَنَا ابْنُ أَبِي عُمَرَ، حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، حَدَّثَنَا مُحَمَّدُ بْنُ الْمُنْكَدِرِ، قَالَ مَرَّ سَلْمَانُ الْفَارِسِيُّ بِشُرَحْبِيلَ بْنِ السِّمْطِ وَهُوَ فِي مُرَابَطٍ لَهُ وَقَدْ شَقَّ عَلَيْهِ وَعَلَى أَصْحَابِهِ قَالَ أَلاَ أُحَدِّثُكَ يَا ابْنَ السِّمْطِ بِحَدِيثٍ سَمِعْتُهُ مِنْ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ بَلَى . قَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ رِبَاطُ يَوْمٍ فِي سَبِيلِ اللَّهِ أَفْضَلُ وَرُبَّمَا قَالَ خَيْرٌ مِنْ صِيَامِ شَهْرٍ وَقِيَامِهِ وَمَنْ مَاتَ فِيهِ وُقِيَ فِتْنَةَ الْقَبْرِ وَنُمِّيَ لَهُ عَمَلُهُ إِلَى يَوْمِ الْقِيَامَةِ . قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ .
Tirmizi
The Book on Virtues of Jihad • Hadith 1713