The unerring of you throws the first rock at her.
Jhn 8:7 He that is without sin among you, let him first cast a stone at her.
Interesting and Hidden Aspects:
As is so often the case, there is a humorous double meaning here.
The verse can be interpreted one of two ways. The common way is to interpret the adjective used as "without sin" or "blameless," but the word also means "unerring" so it could also be interpreted as a challenge to the person in the crowd who never misses to throw the first rock.
The crowd is stopped not only by their sense of guilt, but by a confusion that highlights Christ's first meaning. Is there someone there who thinks that they can throw and not miss? If so, what if they do miss? Then that person will look like a fool, guilty of hubris.
Remember, hubris, foolish pride, was considered the chief sin of Greek culture and the chief cause of the downfall of heroes. It is possible that some of the self-righteous in the crowd considered themselves as morally perfect, but they would not want to put the perfection of their rock throwing skills the test.
The two meanings of "without error" indicating either a perfect person or someone who can throw perfectly.
πρῶτος "First" is from prôtos (protos). In place, this means "the foremost." Of time, it means "the initial." In order, it means "the first." In math, it means the prime numbers. Of rank or degree, it means "the highest" or "the best." This was the word used to mean "the first" in the parable of the landowner hiring workers.
αὐτὴν "Her" is from autos (autos), which means "the same," and the reflexive pronouns, "myself", "yourself", "himself", "herself", "itself," or the oblique case of the pronouns, "him", "her," and "it." It also means "one's true self," that is, "the soul" as opposed to the body and "of one's own accord."