Mishkat al-Masabih 6 Zakat كتاب الزكاة 151

وَعَنْ مَرْثَدِ بْنِ عَبْدِ اللَّهِ قَالَ: حَدَّثَنِي بَعْضِ أَصْحَابِ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَنَّهُ سَمِعَ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ: «إِنَّ ظِلَّ الْمُؤْمِنِ يَوْمَ الْقِيَامَة صدقته» . رَوَاهُ أَحْمد

Marthad b. ‘Abdallah said one of the companions of God’s messenger told him that he had heard him say, “The believer’s shade on the day of resurrection will be his sadaqa .” Ahmad transmitted it.