The New Testament is known today as a Greek book, but much of it was originally written in Hebrew by the Jewish disciples of Yeshua ("Jesus" in Hebrew) nearly 2000 years ago. According to the Book of Acts, Yeshua himself spoke Hebrew. In Acts 26 Paul describes a vision he had on the road to Damascus:
I saw a light from heaven, brighter than the sun, shining around me and my companions. When we had all fallen to the ground, I heard a voice saying to me in the Hebrew language, 'Saul, Saul, why are you persecuting me? It hurts you to kick against the goads.' (Acts 26:12-14)
It would have been just as natural for Yeshua to speak to Paul in Greek. After all, Yeshua certainly knew Greek and Paul was a totally Hellenized Jew who had received Roman citzenship. The fact that the Book of Acts says that Yeshua spoke to Paul in Hebrew testifies to the importance of Hebrew as the language of revelation for New Testament believers. Paul himself preached to the Jews in Hebrew as reported in Acts 21:
When he had given him permission, Paul stood on the steps and motioned to the people for silence; and when there was a great hush, he addressed them in the Hebrew language (Acts 21:40)
New Testament scholars have long known that the Greek of the Greek of the New Testament has a strong Hebraic character to it. Most grammars of New Testament Greek contain an entire category known as Hebraisms
which are Hebraic thought patterns translated very literally into Greek. Five books of the New Testament in particular contain a large number of Hebraisms leaving little doubt they were either written in Hebrew or translated from Hebrew sources. These five books are: Matthew, Mark, Luke, Acts and Revelation. The Hebraisms in these books proves that Yeshua and his original disciples preached in Hebrew and even more importantly that their words were recorded in Hebrew.