The truest word spoken by an Arab (pre-Islamic) in poetry is this verse of Labid: "Behold! apart from Allah everything is vain." (Using translation from Muslim 2256a)
"أَشْعَرُ كَلَمةٍ تَكلَّمَتْ بِهَا الْعَرَبُ كلِمَةُ لَبيدٍ: أَلا كُلَّ شيءٍ مَا خَلا الله بَاطِلٌ" .