Good  weapons are instruments of fear; all creatures hate them.
Therefore followers of the Tao never use them.
The wise man prefers the left,
The man of war prefers the right.
Weapons are instruments of fear; they are not a wise man's tools.
He uses them only when he has no choice.
Pëace and quiet are dear to his heart,
And victory no cause for rejoicing.
If you rejoice in victory, then you delight in killing;
If you delight in killing, you cannot fulfil yourself.
On happy occasions precedence is given to the left,
On sad occasions to the right.
In the army the general stands on the left,
The commander-in-chief on the right.
This means that war is conducted like a funeral.
When many people are being killed,
They should be mourned in heartfelt sorrow.
That is why victory must be observed like a funeral
 This word is missing in the Ma wang tui versions and a source of confusion for some. Cf. below.
 The Ma wang tui text, reads these two lines on rejoicing in victory rather as rejoicing in weapons as beautiful which is in itself tantamount to delighting in instruments of ill omen and in killing.
 Both Lau and the Ma wang tui text agree that this means one cannot realise one's intentions as regards spreading one's ideas.
Interestingly, this and chapter 66 are the only ones that have no commentary by Wang Pi, and - of course - there is much speculation as to why this might be.
Was it - as I felt myself in writing it down - that this chapter seemed to him to be a later interpolation? If so, it certainly existed well before he did (he was born in 226 CE whereas the Ma wang tui texts date from early Han times nearly 500 years before). Or was it simply, as John Lynn suggests, that he felt it was self-evident and didn't need a commentary from him? In fact, in his commentary on ch 63, he cites a line from this chapter (but not brought out as such in the Gia-fu Feng translation), viz., that rather than rejoicing in weapons as beautiful one should instead be utterly dispassionate as regards them,thus showing that he was, indeed, awre of this chapter as it stood. Lynn also mentions that it is quite feasible that the commentary has simply been lost. Henrick's mentions that in some editions of the the Lao-tze, chapters 30 and 31 are brought together as one inasmuch as they seem - at least on the outside - to deal with the same subject.
Professor Cheng's commentary points out that several early commentators were upset by the 'fine' in the first line while others left it withoutout commentary. He himself also suspends judgement.
His commentary then continues as follows: ... the ancients, when they took up arms, believed it to be inauspicious and so used the right side. They did not consider even victory a cause for celebration, but rather mourned the multitudes of slaughtered. That is why chapter 69 says, 'when opposing armies face each other, the one stung by grief will be victorious'.
Inasmuch as it appears, on the surface, simply to repeat what was said in chapter 30, this chapter might well seem to be either redundant or a later interpolation, but - with some reflection, I might add! - another interpretation could be as follows: For some odd reason, weapons are regarded (at least by most men and some women) as beautiful. I note, for example, when demonstrating the sword form of t'ai chi ch'uan, that many are fascinated by it not because of the projection of chi into the instrument so much as because of the beauty of the instrument itself and of its manipulation.
T'ai chi ch'uan and t'ai chi chien(*), however, are both 'rooted in the feet, develop in the legs, find direction in the waist and manifest in the fingers'... What this ultimately means is that it doesn't really matter what you do with the hands as long as they fully manifest what is coming up from the feet through the legs and waist. Calligraphy is a good non-martial example. Or sweeping.
I, too, rather like swords and knives... for various reasons, magical, practical and as extensions of chi... Also because they are often very good examples of their makers' art. I do not, when examining a sword, imagine myself (or anyone else for that matter) cleaving somebody's head with it or sticking it into anyone's softer and less protected parts.
(*) Very roughly translatable as t'ai chi open-handed sparring and t'ai chi sword form.
I am also, I find, very rarely strategic... I respond in the instant rather than think things through to an end I might be seeking... In fact, I find 'desired ends' generally quite undesirable (as in: 'be careful what you wish for; it may just be granted').
What I mean by all this is that for people who like to manipulate and who deem strategy a useful tool in their lives, there is a fascination with the logic of things - the 'straight line' logic of the brain. I believe (having never yet seen a straight line in nature except the seeming ones of light rays which I am assured are actually curved, if over vast distances of space) rather in the 'eco' logic of the 'heart' - the 'heart-mind' mentioned a few chapters back.
I think it's this tendency here that Grandfather Lao is pointing to. The universe is sacred. Anthing you do to 'make it better' can only really make it worse, or, at very best, be of fleeting effect. There is a fascination in thinking you're in control, but who actually ever is? Those who control best are like surfers reading the instant of wave through their feet and bodies and responding 'im-mediate-ly', so to speak - without 'mediating' thought or preprepared 'plan' and 'strategy'. They, at least, are alive to the moment - unless (like myself) they happen to be woolly-minded into the bargain.