بِأَنَّا نُورِدُ الرَّايَاتِ بِيضًا وَنُصْدِرُهُنَّ حُمْرًا قَدْ رَوِينَا
We lead the banners in white and bring them back red, as though they had drunk their fill.
Nūridu and nuṣdiru oppose taking something to water and bringing it back. The language is transferred to banners carried into and out of battle.
Bīḍan and ḥumran describe their respective states. The imagined change from white to red exaggerates bloodshed. The suggestion of having “drunk one’s fill” transfers water imagery to the battlefield; it is not a literal account of banners drinking.