Verse 38

In plain words

So then — hear this teaching, spoken for the man who fights holding that this battle is his own dharma —

Put pleasure and pain on one level — that is what "the same" means here: equal in weight, neither one preferred. And do not let rāga and dveṣa arise toward them at all. Do the same with gain and loss, with victory and defeat. Then take up the battle — "be yoked to it" simply means: apply yourself, get to work. Fight like that, and no sin comes to you. This much of the teaching is said in passing, as the occasion brought it up.

Close to the Sanskrit

There, 'battle is one's own duty' — thus, of one fighting in this way, hear this instruction —

Having made pleasure and pain the same — that is, equal — and also not having produced attraction and aversion: this is the sense. Likewise, having made gain and loss, and victory and defeat, equal, then engage yourself in battle — that is, exert yourself. Fighting in this way, you will not incur sin. Thus this instruction is incidental. (38)

In plain words

“Brother-in-law! You say that to fight is sin. You are badly mistaken! It is refusing to fight, failing to put an end to the sinners, and so bringing harm upon the host of the supremely virtuous, that is sin; by the very act of not fighting you would be committing a great sin. If at this time you abandon your svadharma, you will fall to the lowest state. If you carry out your svadharma, no sin will touch you. Keep an even citta amid the pairs of opposites, and face them in battle with a firm citta.” For this very reason he taught eight ślokas in this chapter, beginning with the thirty-first śloka. In the thirty-seventh śloka he spoke of steadfastness in svadharma, and said that one must take part in karma with an even mind in pleasure and pain. The thirty-ninth śloka is a linking śloka. In it the Paramātma declared: “This has been taught to you in Sāṅkhya”; that is, “I have taught you Sāṅkhya Buddhi. Now I will make known Yoga Buddhi; listen.”