'Root' in the Bible

And even now the axe is put to the root of the trees; every tree then which does not give good fruit is cut down, and put into the fire.

And when the sun was high, it was burned; and because it had no root it became dry and dead.

But having no root in himself, he goes on for a time; and when trouble comes or pain, because of the word, he quickly becomes full of doubts.