Hadith 8:129
Ma'mar reported God's Messenger as saying, “If anyone keeps goods till the price rises he is a sinner.” Muslim transmitted it.
عَن معمر قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مَنِ احْتَكَرَ فَهُوَ خَاطِئٌ» . رَوَاهُ مُسْلِمٌ
Original Reference: Mishkat al-Masabih 2892