Different Kinds of Purity - 7th Purity

The seventh purity is Purity by knowledge and vision (nana-dassana- visuddhi).
When the three moments of adaptation knowledge have fallen away, change- of-lineage knowledge (gotrabhu nana) arises. It has the characteristic of adverting to lokuttara citta, and thus it neither belongs to the sixth purity, purity by knowledge and vision of the path, nor to the seventh purity, purity by knowledge and vision; it is intermediate between these two kinds of purities. Still, it is reckoned as insight knowledge, because it follows the course of insight (Visuddhimaga, Ch. XXII, 1). When change-of-lineage has fallen away, magga-citta arises and then there is purity by knowledge and vision. Thus, there are seven purities in all.