عَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ عَنْ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ: ((إِذَا نُودِيَ لِصَلَاةِ الصُّبْحِ وَأَحَدُكُمْ جُنُبٌ فَلَا يَصُمْ يَوْمَئِذٍ))
It is narrated from Sayyiduna Abu Hurairah, may Allah be pleased with him, that the Messenger of Allah, peace and blessings be upon him, said: When the call to prayer for Fajr is given and any of you is in a state of major ritual impurity (junub), then he should not fast that day.