The five khandhas are things to be understood (pariññeyyā dhammā). S.iii.26.
The teaching for the comprehension of all attachment: from eye and object arises eye consciousness, the union of these is contact; from contact comes feeling; similarly with regard to the other senses. S.iv.32f.
The five indriyas, if developed, conduce to comprehension of the way out. S.v.236.
By fully understanding body, feeling, etc., deathlessness is realized. S.v.182.