'Themselves' in the Bible

But these, whatever things they know not, they speak railingly against; but what even, as the irrational animals, they understand by mere nature, in these things they corrupt themselves.

Woe to them! because they have gone in the way of Cain, and given themselves up to the error of Balaam for reward, and perished in the gainsaying of Core.

These are spots in your love-feasts, feasting together with you without fear, pasturing themselves; clouds without water, carried along by the winds; autumnal trees, without fruit, twice dead, rooted up;

These are they who set themselves apart, natural men, not having the Spirit.