To "speak with a word" seems to me in this context to be the simplest
meaning and thus close to the idea of "binding with fetters and chains" (Mk
5:4), or "by this means" (with prep. EN) we know that we know him (I John
2:3). Sometimes we let English determine the function in Greek. This
would be the same function as in Matt 8:16 where the evangelists reported
EXEBALEN TA PNEUMATA LOGWi, "He cast out the (evil) spirits with a word.
The concept of the authority of his word is what is being emphasized in
both context.