Sayyidah Aishah (may Allah be pleased with her) narrates from the Prophet (peace and blessings be upon him) that he (peace and blessings be upon him) said: "Whoever does not make the intention to fast before the break of dawn, there is no fast for him."
Al-Daraqutni said: Abdullah bin Abbad alone narrated it from al-Mufaddal with this chain, and all of them are trustworthy (thiqat).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 7912