What did Jesus quote from when He quoted the Old Testament and did not use Hebrew?
When Jesus quoted the Old Testament without using Hebrew, He quoted from the Septuagint, the Greek translation of the Hebrew Old Testament made by 70 Jewish scholars before Christ. That Greek version is the source He referred to, and it is why Greek scholars value the Septuagint for study.
Les explains that the Septuagint was the Old Testament Hebrew translated into Greek by 70 Jewish scholars quite a few years before Christ. He put a lot of emphasis on the Septuagint because that was the Greek Jesus always referred to. Whenever Jesus would quote from the Old Testament, if He did not quote it in the Hebrew, He would quote it from the Septuagint Greek. Les also notes that this is where a lot of Greek scholars put the Greek language together for our own benefit. This came up while he was checking the Greek word behind "corrupt" in Ephesians, using the Greek and Strong's Concordance, and then looking it up in the Septuagint.