Hans Peter L’Orange has in my opinion convincingly demonstrated that the gesture in general expressed the spoken
word and was a sign of logos during the Roman Empire and Late Antique periods, but the gesture had nothing to do with what was said or taught.12
...
All the bronze hands of Sabazios date to the Roman Imperial period and the earliest examples are from military camps, and it is plausible that the phenomenon of bronze hands sur-
mounted on poles was diffused throughout the Roman Empire to a large extent by Roman soldiers.27 The bronze hand from the military camp at Dangstetten, dating to the Augus-
tan period is the earliest-known example.28 Besides the Roman
military camps the hands are most frequently found in Italy, at
sites such as Pompeii.29 The distribution of the bronze hands
differs somewhat from where the cult is otherwise attested.30
It is noteworthy that no hands are known at all from Lydia,
from where we have a large attestation of the cult.31 There are
very few hands from the eastern part of the Mediterranean,
i.e. from Greece and Asia Minor. There are only three known
examples of hands from Asia Minor: a bronze hand from An-
talya/Attaleia in Pamphylia, a bronze hand said to be from
Caesarea in Cappadocia,32 and a third hand found on top of a
bone pin, possibly a hair pin, from Gordion in Phrygia.33 The
head of the pin was carved in the shape of a left hand and it
was found complete except for three digits that were broken
off: the thumb, and index and middle fingers (Figs. 3 & 4).
These three digits were originally extended, while the outer
two fingers were folded, which is the same gesture as that of
the Sabazios hands. It came from a 4th-century BC context
in the city mound, where it was found in a pit together with a
black-glazed fish plate and a coin of Lysimachus. We are not in
the position to identify it as part of the Sabazios cult, since the
hand carries none of the characteristic symbols, which may be
due to it being much earlier in date than the bronze hands.34
The bone pin is not unique as a few more examples with
hands are known, two from Sardinia, and one from Cyprus,
likewise interpreted as hair pins.
...
The gesture was later adopted by the Early Christians in their ico-
nography of Christ and his disciples and L’Orange (1953, 171–197, esp.
171–175, figs. 120–123) has demonstrated that the benedictio Latina
gesture originally indicated the spoken word.