لعمرك ما أدري وإني لأوجل على أينا تعدو المنية أول
By your life, I do not know – though certainly I assuredly dread – on which of us will the fate [of death] strike first
Meaning: He is saying to his companion: I swear to you by your life I certainly do not know – though I am afraid – whom amongst us will death befall before it befalls his companion.
What the poet means is that this life is short and a person is prone to death at every moment, so it is unbefitting that we spend our lives in abandonment and severance.
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