While it is possible that Jesus and some of his apostles knew and used Greek (at least on certain occasions), it is clear that their primary language of communication was Aramaic and, quite possibly, Hebrew as well. Here is the key evidence.
The New Testament records several unmistakable instances of Aramaic usage. Most notable is Mark 5:41, where Jesus raises Jairus’ daughter from the dead with the command, Talitha koum[i](“Little girl, get up!”). Interestingly, if Peter spoke in Aramaic when he raised Tabitha from the dead, he would have used almost the exact same phrase: Tabitha koum[i] (see Acts 9:40). Other examples of Aramaic on the lips of Yeshua include His words on the cross from Psalm 22:1, quoted in Matthew 27:45, “Eloi, Eloi, lama sabachthani?” Acts 1:19 also provides a good example of Aramaic usage, since it speaks of the field in Jerusalem purchased by Judas Iscariot, and states that the people “called that field in their language Akeldama, that is, Field of Blood.” This name, Akeldama, reflects the Aramaic words haqal dama’, field of blood, and is definitely not a Hebrew construction.
Despite the attempts of some “Hebrew only” authors to downplay or eliminate these examples, they clearly point to Aramaic usage by Jesus and His followers. Given the first century, Galilean background of the Lord and His disciples, Aramaic usage would make perfect sense and would be in keeping with the prevailing scholarly consensus.
There are many other Aramaic names and terms in the New Testament (such as Abba andGolgotha) but they do not “prove” that Aramaic was commonly used anymore than Native American place names on Long Island, New York, such as Copiague and Setauket and Nesconset “prove” that Long Islanders speak American Indian dialects. There is, however, one key Aramaic phrase preserved in the Greek New Testament indicating its importance to the early believers. It is the word Maranatha, which is Aramaic, not Greek, and which most likely means, “Our Lord, come!” (1 Corinthians 16:22; it could also be translated, “Our Lord has come,” or, “O Lord, come!”) The fact that Paul could use this expression in a letter to Greek speakers (who would not have known Aramaic) points to the widespread usage of Aramaic among the early Judean and Galilean disciples.
The New Testament points to at least some of the apostles speaking Greek. New Testament scholar Richard Bauckham notes that “Peter was surely able to speak Greek,” adding, “In light of Peter’s early life in the dominantly Gentile context of Bethsaida, Markus Bockmuehl speaks of ‘a very strong likelihood that Peter grew up fully bilingual in a Jewish minority setting.’” Bauckham also notes, “On the other hand, it is worth noting that Philip, also from Bethsaida, and Peter’s brother Andrew, rather than Peter himself, are regarded as the disciples most proficient in Greek in John 12:21-22,” where it is recorded, beginning in John 12:20, that some Greek speaking Jews wanted to see Jesus: “They came to Philip, who was from Bethsaida in Galilee, with a request,” indicating that he was known to them or referred to them as a Greek speaker. Many scholars also believe that Peter preached in Greek in Acts 2, which would have been the most widely understood language by the Jews from many different countries.
Acts 6 also provides possible evidence that, side by side with Aramaic-speaking (or Hebrew-speaking) widows, there were Greek-speaking widows, all part of the same believing community in Jerusalem. It is possible, however, that Acts 6:1 refers to Hellenized Jews rather than Greek-speaking Jews, although it is likely that these Hellenized Jews spoke Greek. Another perspective is brought by New Testament commentator Craig Keener: “Some scholars think that the ‘Hellenists’ (NRSV) here are simply Greek-speaking Palestinian Jews, but most Jews in Palestine were bilingual, and Greek was probably the first language for most Jerusalemites. The more likely proposal is that this text refers to Diaspora Jews who have settled in Jerusalem, as opposed to natives of Jewish Palestine.” This observation, however, only underscores the widespread usage of Greek in the land of Israel in the days of Jesus.
There is also evidence for the use of Hebrew by Jesus and His disciples. At the turn of the twentieth century, many non-Jewish scholars thought that Hebrew had basically become a dead language at least one or two centuries B.C.—a dead language, that is, as far as being a spoken language, since no one argued that Hebrew was not still used as a written, holy language during this time. Archeological discoveries in the last century, however, raised serious questions about this assumption—obviously, we have no recordings of speeches or conversations from the first century A.D., but certain archeological findings can point to common language usage in a given society—while many Jewish scholars had recognized that Hebrew had not entirely died out as a spoken language 2,000 years ago.
As stated by the editors of a recent volume seeking to shed light on the words of Jesus,
Jesus certainly knew and spoke Aramaic when needed, but many scholars now believe that he did his teaching in Hebrew. The rabbis of Jesus’ day and for hundreds of years after him delivered their parables, legal rulings, prayers and sermons entirely in Hebrew. In fact, there are several thousand parables and prayers recorded in rabbinic literature, and virtually all are in Hebrew. This Hebrew was not the dialect of the Scriptures, but a newer, living language called Middle or Mishnaic Hebrew. If Jesus functioned within Jewish society, he most likely delivered his teachings in Hebrew as well. Evidence for this comes from the fact that many Semitic idioms found in Jesus’ stories and teachings translate well into Mishnaic Hebrew, but don’t make sense in Aramaic at all.
In terms of the last sentence, there are Aramaic scholars who claim that the opposite is true, and that many Semitic idioms found in Jesus’ stories and teachings translate well into Aramaic, but don’t make sense in Hebrew. The rest of the paragraph, however, raises some excellent points, suggesting—but still not proving—that when Jesus dialogued and debated with the religious leaders in Jerusalem, He may have done so primarily in Hebrew (or, as reflected in the later Talmudic literature, in both Hebrew and Aramaic). This would also suggest that when the New Testament speaks of the “Hebrew language” (hebraidi dialekto) it actually means Hebrew and not Aramaic, as many translators and commentators have believed (see Acts 21:40; 22:2, referring to Paul’s speech; 26:14, referring to Yeshua addressing him on the road to Damascus; contrast the NRSV, which has “Hebrew” in the text, with the NIV, which has “Aramaic” in the text and “Hebrew” in the marginal notes). The question, however, is not so simple, as I pointed out in a somewhat technical article published in 1993, and “Hebrew” can simply mean, “the language spoken by the Jewish people,” meaning Aramaic rather than Hebrew. Other scholars have questioned whether a large Jewish audience in Jerusalem could have been expected to understand Paul preaching in Hebrew rather than Aramaic, while others, as noted above, have suggested that Peter must have preached in Greek in Acts 2, since that language would have been more widely understood than even Aramaic by the visiting Jews.
There are, however, some internal indications within the New Testament text that could point to Hebrew usage (although others claim that the indications point to Aramaic usage), and so some level of Hebrew usage cannot be ruled out, although those who argue that the key to rightly understanding the New Testament is reconstructing the alleged Hebrew original are certainly mistaken.
So, what language did Jesus and the apostles speak? As a whole, primarily Aramaic, at least in everyday use, in teaching settings, possibly, Hebrew and in other cases Greek (although this is not to say that the Lord and the apostles were all able to speak three languages).