فَاصْدَعْ بِمَا تُؤْمَرُ
Proclaim clearly what you are commanded to convey.
Ṣadʿ has a sensory meaning associated with cracking or splitting something solid, such as glass. The image is borrowed for the decisive, open declaration of a commanded message, a conceptual communicative act.
Source: the physical splitting of a solid object.
Target: making the command manifest through proclamation.
Common feature: overcoming concealment or obstruction so that something becomes openly manifest; an intellectual relation.