1: Cleansing of morality takes place in 2 ways: by understanding the misery of moral deviation sila-vipatti see. vipatti and by understanding the blessing of moral perfection sila-sampatti see: Vis.M I.
2: Cleansing of concentration is concentration connected with progress visesa-bhāgiya-samādhi hāna-bhāgiya If, for example, one has entered the 1st absorption, and sense-perceptions and reflections arise, in that case there is concentration connected with decline... If, however, perceptions and reflections free from thought-conception and discursive thinking 2nd jhāna arise, in that case there is concentration connected with progress.
3: Cleansing, with reference to understanding, is identical with the 'insight leading to the path ascent' vutthāna-gāminī-vipassanā, which arises at the stage of 'purification by knowledge and vision of the path-progress' see: visuddhi VI, and is followed immediately by the change-of-lineage moment and the entrance into the supra-mundane paths.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.