Bulugh al-Maram, Book 15, Hadith 1436 (In-Book)

Sahl bin Hunaif (RAA) narrated that the Messenger of Allah said: “He who assists a Mujahid for Allah’s sake, a debtor who is in distress (being unable to pay his debt) or a slave who had made an agreement to buy his freedom, Allah will shade him, with His Shade, on the Day when there will be no shade but His.” Related by Ahmad and Al- Hakim graded it as Sahih.

وَعَنْ سَهْلِ بْنِ حُنَيْفٍ ‏- رضى الله عنه ‏- أَنَّ رَسُولَ اَللَّهِ ‏- صلى الله عليه وسلم ‏-قَالَ: { مَنْ أَعَانَ مُجَاهِدًا فِي سَبِيلِ اَللَّهِ, أَوْ غَارِمًا فِي عُسْرَتِهِ, أَوْ مُكَاتَبًا فِي رَقَبَتِهِ, أَظَلَّهُ اَللَّهُ يَوْمَ لَا ظِلَّ إِلَّا ظِلُّهُ } رَوَاهُ أَحْمَدُ, وَصَحَّحَهُ اَلْحَاكِم ُ 1‏.‏ ‏1 ‏- ضعيف.‏ رواه أحمد (3 / 487)‏، والحاكم (2 / 89‏- 90 و 217)‏ وفي سنده عبد الله بن سهل بن حنيف، وهو مجهول.‏

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also referenced under: Book 15, Hadith 1480 (English)