a leopard cannot change its spots; the child is father to the man; (lit.) the soul of a child of three (is the same) at 100
to turn over a new leaf; to reform (oneself)
tread on a worm and it will turn; even a tiny bug will defend itself; even the weakest and smallest beings have their own wills, so do not make light of them
Dead Souls (novel by Gogol); Myortvye dushi
(theory of) the immortality of the soul