On the subject of enemies the "Havamal" gives not a little curious advice: A man should never step a foot beyond his weapons; for he can never tell where, on his path without, he may need his spear.
A man, before he goes into a house, should look to and espy all the doorways (_so that he can find his way out quickly again_), for he can never know where foes may be sitting in another man's house.
Does not this remind us of the Japanese proverb that everybody has three enemies outside of his own door?
But the meaning of the "Havamal" teaching is much more sinister.

And when the man goes into the house, he is still told to be extremely watchful--to keep his ears and eyes open so that he may not be taken by surprise: The wary guest keeps watchful silence; he listens with his ears and peers about with his eyes; thus does every wise man look about him.
One would think that men must have had very strong nerves to take comfort under such circumstances, but the poet tells us that the man who can enjoy nothing must be both a coward and a fool.

Although a man was to keep watch to protect his life, that was not a reason why he should be afraid of losing it.

There were but three things of which a man should be particularly afraid.

The first was drink--because drink often caused a man to lose control of his temper; the second was another man's wife--repeatedly the reader is warned never to make love to another man's wife; and the third was thieves--men who would pretend friendship for the purpose of killing and stealing, The man who could keep constant watch over himself and his surroundings was, of course, likely to have the longest life.
Now in all countries there is a great deal of ethical teaching, and always has been, on the subject of speech.