أَلَا لَا يَحِلُّ مَالُ امْرِئٍ إِلَّا بِطِيبِ نَفْسٍ مِنْهُ
A person’s property is not lawful without willing consent.
أَلَا attracts attention; لَا negates; and إِلَّا introduces an exception or condition. Translating them all as “not” would lose the structure of the sentence.
Consider “Take heed: this cannot be taken without permission.” “Take heed” captures attention, “cannot” negates, and “without permission” states a condition. The Arabic forms play distinct roles.