। ॥
In plain words
As a rule, words that command carry a push in them — that is what they do, in everyday speech and in the Veda alike. But how could that push belong to words like "tat tvam asi," which do nothing but make known what is already the case?
Close to the Sanskrit
As a general rule, the action-instigating force of injunctive statements is observed in ordinary usage and in the Veda. How could that belong to [a statement] that makes known an already-established fact — to 'tat tvam asi' and the rest?