Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) said: Eat the pomegranate with its pith! For it is a tanning for the stomach.
Ahmad recorded it, and its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطب / 8351