Hadith 8:135
Abu Umama reported God’s Messenger as saying, “If anyone hoards grain for forty days and then gives it in sadaqa , that will not act as an atonement for him.” Razin transmitted it.
وَعَنْ أَبِي أُمَامَةَ: أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «مَنِ احْتَكَرَ طَعَامًا أَرْبَعِينَ يَوْمًا ثمَّ تَصَدَّقَ بِهِ لَمْ يَكُنْ لَهُ كَفَّارَةً» . رَوَاهُ رزين
Original Reference: Mishkat al-Masabih 2898