Narrated 'Aishah (RA):

al-Aqra' is the period of a woman's purity (which occurs between two menses). [Malik, Ahmad and an-Nasa'i reported it in the course of a story with a Sahih (authentic) chain of narrators].

وَعَنْ عَائِشَةَ رَضِيَ اَللَّهُ عَنْهَا قَالَتْ: { إِنَّمَا اَلْأَقْرَاءُ; اَلْأَطْهَارُ } .‏ أَخْرَجَهُ مَالِكٌ فِي قِصَّةٍ بِسَنَدٍ صَحِيحٍ [1]‏ .‏