عَنْ حَفْصَةَ (زَوْجِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ وَرَضِيَ اللَّهُ عَنْهَا) عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ أَنَّهُ قَالَ: ((مَنْ لَمْ يُجْمِعِ الصِّيَامَ مَعَ الْفَجْرِ فَلَا صِيَامَ لَهُ))
It is narrated from the wife of the Messenger, Sayyida Hafsa (may Allah be pleased with her), that the Noble Prophet (peace and blessings be upon him) said: Whoever does not make the intention to fast before Fajr, there is no fast for him.