But, if you will not fight this righteous war, then, having abandoned your own duty and fame, you shall incur sin.

atha = therefore; cet = if; tvaṃ = you; imaṃ = this; dharmyaṃ = as a religious duty; saṃgrāmaṃ = fighting; na = do not; kariṣyasi = perform; tataḥ = then; svadharmaṃ = your religious duty; kīrtiṃ = reputation; ca = also; hitvā = losing; pāpaṃ = sinful reaction; avāpsyasi = will gain.;