Question:
If a menstruating or post-natal woman becomes pure before Fajr and performs ghusl after Fajr, will her fast be valid or not?
Answer:
Yes. If a menstruating woman becomes pure before Fajr and performs ghusl after the break of dawn, her fast will be valid. The same ruling applies to a woman in post-natal bleeding, because at that time she is counted among those eligible to fast, and she is like the one who is overtaken by dawn in a state of janabah. Indeed, her fast is correct, because Allah the Exalted says:
فَالْآنَ بَاشِرُوهُنَّ وَابْتَغُوا مَا كَتَبَ اللَّهُ لَكُمْ ۚ وَكُلُوا وَاشْرَبُوا حَتَّىٰ يَتَبَيَّنَ لَكُمُ الْخَيْطُ الْأَبْيَضُ مِنَ الْخَيْطِ الْأَسْوَدِ مِنَ الْفَجْرِ
“So now, have relations with them and seek what Allah has decreed for you, and eat and drink until the white thread becomes distinct to you from the black thread of dawn.”
Since Allah has permitted intercourse until the break of dawn, it follows that the ghusl of janabah is performed only after the break of dawn.
Also, there is the hadith of Aisha (may Allah be pleased with her):
أن النبى صلى الله عليه وسلم ، كان يصبح جنبا وهو صائم
“Indeed, the Prophet ﷺ would enter the morning in a state of janabah from intercourse with his wife, and he would then fast.”
That is, the Prophet ﷺ would perform the ghusl of janabah after the break of dawn.
