«فَإِذَا جَاءَ أَجَلُهُمْ لَا يَسْتَأْخِرُونَ سَاعَةً وَلَا يَسْتَقْدِمُونَ»
When their appointed term comes, they can neither delay it for an hour nor advance it. (Qurʾān 7:34)
Idhā jāʾa ajaluhum establishes a temporal conditional setting; lā yastaʾkhirūn conveys its consequence. Analysing wa-lā yastaqdimūn requires attention to how both negations bear upon the appointed term and the scope of the conditional framework.
The intended unity is the impossibility of altering the assigned time, whether by delay or anticipation.