Mu'ammal bin Isma'il narrates from Sufyan (may Allah have mercy on him), and he added these words: "When you see the new moon at the beginning of the day, do not break your fast until two upright men testify that they sighted it the previous evening."
Abu Bakr (al-Naysaburi) said: If Mu'ammal has preserved it, then it is gharib (unusual); the imam Abd al-Rahman bin Mahdi contradicted him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 7983