{He supposed} (enomizen). Imperfect active of 
omiz(935c). He
was supposing, Stephen explains, when he smote the Egyptian.
{That his brethren understood} (sunienai tous adelphous).
Present active infinitive of suni(886d)i, to send (put) together,
to grasp, to comprehend, in indirect discourse with the
accusative of general reference. {By his hand was giving them
deliverance} (dia cheiros autou did(9373)in sot(8872)ian autois).
Picturesque use of "hand" as in  2:23 , present active indicative
of did(936d)i retained in indirect discourse after imperfect
enomizen. But they understood not (hoi de ou sun(886b)an). Page
notes "the rhetorical power of these words" from Stephen.
Sun(886b)an (first aorist indicative, k aorist) refers to
sunienai just before.