Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
darimi:866Ḥajjāj > Ḥammād > Yūnus > al-Ḥasan > Idhā Raʾat al-Dam Faʾinnahā Tumsik

[Machine] Regarding prayer, one's menstruation period is counted as either one day or two days, and after that, she is considered to be in a state of istihaadah (bleeding outside the menstrual period).  

الدارمي:٨٦٦أَخْبَرَنَا حَجَّاجٌ حَدَّثَنَا حَمَّادٌ عَنْ يُونُسَ عَنِ الْحَسَنِ قَالَ «إِذَا رَأَتِ الدَّمَ فَإِنَّهَا تُمْسِكُ

عَنِ الصَّلَاةِ تَعُدُّ أَيَّامَ حَيْضِهَا يَوْمًا أَوْ يَوْمَيْنِ ثُمَّ هِيَ بَعْدَ ذَلِكَ مُسْتَحَاضَةٌ»