COMMENTARY on 47:30
A. Yusuf Ali:

Translation:
Had We so wiled, We could have shown them up to you, and you shouldst have known them 4854 by their marks: but surely you wilt know them by the tone of their speech! And Allah knows all that you do.
Commentary:

4854  Evil is not always necessarily branded in this life with a distinguishing mark or brand. But the discerning ones know. Evil is betrayed by its speech and behaviour.

 

Muhammad Asad:

Translation:
Now had We so willed, We could have shown them clearly to thee, so that thou wouldst know them for sure as by a visible mark: 35 but [even so,] thou wilt most certainly recognize them by the tone of their voice. 36 And God knows all that you do, [O men;]
Commentary:
35  Lit., "by their marks": implying, elliptically, that God does not grant to anyone a clear insight, as by a visible mark, into another human being’s heart or mind.
36  Lit., "the tone (lahn) of speech": indicating that a true believer recognizes hypocrisy even without a "visible mark" (sima).