What is relied upon to determine purity from menstruation: is it the emission of a white discharge (whether liquid or thick), and is it necessary to repeat ghusl and prayer upon seeing the usual discharge after having performed ghusl, based on "we did not consider yellowish or brownish discharge after achieving purity to be of any significance"?

A woman recognizes purity from menstruation by one of two signs: dryness (al-jufuf) or the white discharge (al-qassah al-bayda'). If she sees purity by one of these, ghusl (ritual bath) becomes obligatory upon her. If she then sees blood after that – like a reddish discharge – she reverts to being a menstruating woman, provided that this occurs within the period when menstruation is possible, and she must perform ghusl when the bleeding stops. As for yellowish or brownish discharge after seeing purity, it is not considered menstruation unless it occurs within the customary period. If she sees purity by dryness and performs ghusl, then sees the other sign of purity, she is not required to repeat ghusl.