It was narrated from Umm Bakr that:
She was told that 'Aishah said: "The Messenger of Allah said concerning a woman who sees that which causes her doubt (i.e. some bleeding) after she becomes pure: 'That is a vein or veins.'" (Da'if)"What was meant by 'after becomes pure' is after having a bath (following the end of her period)." (DE)
English reference (DE): Vol. 1, Book 1, Hadith 646 (DE)
Arabic reference (DE): Book 1, Hadith 689 (DE)