Sunan Ibn Majah, Chapter: The Chapters Regarding Zakat

"The Messenger of Allah (saw) went out, and a man had hung up one or more bunches of dates. He (the Prophet (saw)) had a stick in his hand and he started hitting that bunch of dates repeatedly, saying: 'If the owner of these dates wanted to give in charity, he should have given something better than these. The owner of this charity will eat rotten and shriveled dates on the Day of Resurrection.' " Sahih