Mishkat al-Masabih 9 Supplications كتاب الدعوات 128

وَعَنْ عَبْدِ اللَّهِ بْنِ عَبَّاسٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مَا الْمَيِّتُ فِي الْقَبْرِ إِلَّا كَالْغَرِيقِ الْمُتَغَوِّثِ يَنْتَظِرُ دَعْوَةً تَلْحَقُهُ مِنْ أَبٍ أَوْ أُمٍّ أَوْ أَخٍ أَوْ صَدِيقٍ فَإِذَا لَحِقَتْهُ كَانَ أَحَبَّ إِلَيْهِ مِنَ الدُّنْيَا وَمَا فِيهَا وَإِنَّ اللَّهَ تَعَالَى لَيُدْخِلُ عَلَى أَهْلِ الْقُبُورِ مِنْ دُعَاءِ أَهْلِ الْأَرْضِ أَمْثَالَ الْجِبَالِ وَإِنَّ هَدِيَّةَ الْأَحْيَاءِ إِلَى الْأَمْوَاتِ الِاسْتِغْفَارُ لَهُمْ» . رَوَاهُ الْبَيْهَقِيُّ فِي شعب الْإِيمَان

‘Abdallah b. ‘Abbas reported God’s messenger as saying, “A dead man in his grave is just like a drowning man calling for help, for he hopes that a supplication from a father, a mother, a brother, or a friend may reach him, and when it does it is dearer to him than the world and what it contains. God most high brings to those who are in the graves blessings several times as great as the size of the mountains because of the supplication of those who are on the earth. The gift of the living to the dead is to ask pardon for them.” Baihaqi transmitted it in Shu’ab al-iman .