«أَرْسَلْتُ الْعُيُونَ»
I sent watchers or spies.
«عُيُون» literally means eyes. Eyes are part of people whose function is to observe and collect information. Thus a bodily part stands for the whole person.
The verb “sent” and the investigative setting guide the reading. For juz'iyya, the literal referent must be a part of the intended whole, rather than merely something associated with it.