وَكُنَّا الْأَيْمَنِينَ إِذَا الْتَقَيْنَا وَكَانَ الْأَيْسَرِينَ بَنُو أَبِينَا
When the forces met, we held the right wing, while our kinsmen held the left.
Al-aymanīn denotes the right wing and al-aysarīn the left wing of an army, not different moral ranks. Banū abīnā refers to kin who share the speaker's ancestry.
The two wings had distinct battlefield positions. By pairing them, the poem presents the force as coordinated and united.