عَلَيْنَا الْبِيضُ وَالْيَلْبُ الْيَمَانِي وَأَسْيَافٌ يَقُمْنَ وَيَنْحَنِينَا
We wear shining helmets and Yemeni protective armour, and carry swords that stand straight yet bend when they strike.
Al-bīḍ here means bright helmets, not merely the colour white; al-yalb al-yamānī denotes protective equipment associated with Yemen.
Yaqmna wa-yanḥanīnā juxtaposes standing straight and bending. In context, the verbs picture the resilience and movement of swords in action. It is martial boasting in poetry, not a technical instruction.