I don't pretend to be an expert in this area, but it is an area I am
interested in, so I will just make a few observations:
1. Most of Jesus' conversations happened in Aramaic. Perhaps also in
Hebrew, as there are a few scholars now who believe the evidence for the
continuation of Hebrew as a spoken language into the Christian era is
sufficient for them to say it is highly probable, at least for Jerusalem and
the surrounding area. Therefore, at least in recorded conversations, the
idioms are very likely to be Aramaic.
2. Only the Gospel of Matthew has been put forward by most scholars as
having a 'Hebrew' [more likely an Aramaic] original. Many people seem to
confuse these two languages. Aramaic was the language of Galilee, and
Jesus' native language. Even if Hebrew still existed as a spoken language,
Aramaic was still the public language of the whole Palestinian-Syrian
3. There were almost certainly collections of the sayings of Jesus, and
these were almost certainly in both Greek and Aramaic. They are likely to
have been used by the gospel writers, especially Luke.
4. Outside the gospels, there are no good reasons [and very few bad
reasons] to suppose there was a non-Greek original for any of the NT books.
5. Even the books written in Greek were written by writers who were almost
certainly more at home in Aramaic. Paul [or perhaps his secretary?] and
Luke both had an excellent command of common Greek, and as they wrote for a
Greek-speaking audience, the occurrence of untranslated Aramaic idioms is
likely to be small.
6. To know when an idiom is Hebrew/Aramaic, when it is an Aramaic/Hebrew
idiom translated into a similar Greek idiom by writers familiar with both,
or when it is a native Greek idiom is beyond the ability of all but a few
scholars who are experts in all 3 languages. For us laymen, attempting to
do so on our own is definitely to run foul of the old saying "a little
knowledge is a dangerous thing".
Marchita (such a pretty name) the New Testament was written in Greek -
the language of the day. Hebrew had bee a dead language for over five
hundred years. When the Israelites returned from Babylonian captivity,
they were speaking Aramaic. In Nehemiah 8 we have first translation from
Hebrew into Aramaic, so everyone could understand.
Of course, just like Latin is a dead language but still studied, Hebrew
was still being taught in the rabbinic schools at the time of Christ -
Jesus probably could read Hebrew - the priests were surprised at his
ability having never attended their schools. St. Paul surely knew his
Hebrew - even though he frequently quoted from the Septuagint - a Greek
translation of the O.T. books. There wasn't an O.T. such as we know it
in Christ's day.