Whether Perfect Ones appear in the world, or whether Perfect Ones do not appear in the world, it still remains a firm condition, an immutable fact and fixed law: that all constructions are impermanent, that all constructions are subject to suffering, that everything is without a self A. III, 134.
What do you think, o Bhikkhus: Is materiality rūpa permanent or impermanent? - Impermanent, o Venerable One. - Are feeling vedanā perception saññā mental constructions sankhāra and consciousness viññāna permanent or impermanent? - Impermanent, o Venerable One.
But that which is impermanent, is it something pleasant or painful? - It is painful, o Venerable One.
But, of what is impermanent, painful and subject to change, could it be rightly said, 'This belongs to me, this am I, this is my ego'? - No, Venerable One.
'I'herefore, whatever there is of materiality, feeling, perception, mental constructions and consciousness, whether past, present or future, one's own or external, gross or subtle, lofty or low, far or near, of all these things one should understand, according to reality and true understanding: 'This does not belong to me, this am I not, this is not my ego'S. XXII, 59.
In one who understands eye, ear, nose, tongue, body and all the remaining constructions as impermanent, painful and no-self, in him the mental chains samyojana are dissolved; S. XXXV, 53.
It is the full comprehension of the 3 characteristics by direct meditative experience which constitutes liberating insight.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.