Hadithcore
Mishkat al-Masabih, 2898

Abu Umama reported God’s Messenger as saying, “If anyone hoards grain for forty days and then gives it in <i>sadaqa</i>, 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

References1 variant
In-Book Reference
Book 11, Hadith 135