عَنْ إِسْحَاقَ بْنِ عَبْدِ اللَّهِ عَنْ أُمِّ الدَّرْدَاءِ رَضِيَ اللَّهُ عَنْهَا تَرْفَعُ الْحَدِيثَ قَالَتْ مَنْ رَابَطَ فِي شَيْءٍ مِنْ سَوَاحِلِ الْمُسْلِمِينَ ثَلَاثَةَ أَيَّامٍ أَجْزَأَتْ عَنْهُ رِبَاطَ سَنَةٍ
It is narrated from Sayyida Umm Darda’ (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) said: Whoever keeps watch over any of the frontier areas of the Muslims for three days, it will suffice him as the reward of one year of ribat (guarding the frontier).