Sahih al-Bukhari 326

Arabic

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا إِسْمَاعِيلُ، عَنْ أَيُّوبَ، عَنْ مُحَمَّدٍ، عَنْ أُمِّ عَطِيَّةَ، قَالَتْ كُنَّا لاَ نَعُدُّ الْكُدْرَةَ وَالصُّفْرَةَ شَيْئًا‏.‏

English translation

Narrated Um `Atiya:We never considered yellowish discharge as a thing of importance (as menses)

Reference: Sahih al-Bukhari 326, Book of Menstrual Periods. English translation by Dr. Muhammad Muhsin Khan.