Riyad as-Salihin, The Book of Virtues, Book 8, Hadith 237
Chapter: The Prohibition of Observing Saum (Fasting) after the Middle of Sha'ban
'Ammar bin Yasir (May Allah be pleased with them) reported:
He who observes the fast on a doubtful day, has in fact disobeyed Abul-Qasim, (i.e., Messenger of Allah (ﷺ)). [Abu Dawud and At- Tirmidhi].











