Hadith.1939 - Safwan ibn Yahya narrated from Al-'Is ibn al-Qasim, who said
"I asked Abu Abdullah (as) about a man who, during the Month of Ramadan, went out while his companions were taking suhoor (pre-dawn meal) in a house. He saw the dawn and called out to them, saying that the dawn had risen. Some of them stopped eating, while others thought he was joking and continued to eat.
Imam (as) said: 'They must complete their fast and make up another day.'"