There is a common objection I have heard from Muslims that the Bible cannot be trusted because it does not preserve the words of Jesus in the language He actually spoke. Jesus spoke Aramaic, they point out, and the words of Jesus in the Gospels are written in Greek. This, they say, casts doubt on the reliability of anything the Gospels say about Jesus. This argument falls flat for a number of reasons.
First of all, this is an absurd objection coming from a Muslim as it would also refute the authority of the Quran! The Quran records words allegedly spoken by Jesus that cannot be found in the Bible or any other ancient document. In what language does it give us these supposed words of Jesus? Arabic, not Aramaic. But Jesus did not speak Arabic. Therefore, the Quran does not preserve the words of Jesus in the language He actually spoke, which (by the logic of this Muslim argument) proves the Quran also to be false. Indeed, this isn't only true of Jesus. None of the biblical and historical figures included in the Quran spoke Arabic, and yet all the words attributed to them in the Quran are in Arabic. If the Muslim argument here were sound, pretty much every narrative in the Quran would be refuted by it.
The fundamental bad assumption is that all translation from one language to another, even translation inspired by the Holy Spirit of God Himself, is inaccurate and untrustworthy. But this simply isn't true. Even skilled humans can accurately translate one language to another, and certainly an almighty God is capable of a task so relatively simple. So even in places where the Bible may report in Greek words that were originally spoken in Aramaic, Hebrew, or some other ancient language, that is not a reason to automatically doubt their veracity.
It should be further noted that Jesus was almost certainly multi-lingual. As a first-century Galilean Jew, Jesus clearly never spoke Arabic, but when we look at the details of His life and ministry, it is highly likely that Jesus knew at least some Greek. Thus, some of the words of Jesus reported in the New Testament (particularly those in certain public discourses with mixed crowds and conversations with Gentiles in non-Jewish regions) might be words that Jesus actually said in Greek to begin with, thus further undercutting the objection.
The New Testament writers also occasionally recorded some of Jesus' words in Aramaic. For example, when Jesus was raising the daughter of Jairus, we read:
"Taking the child by the hand, He said to her, 'Talitha kum!' (which translated means, 'Little girl, I say to you, get up!')," (Mark 5:41).
Likewise, when He was healing a person who was deaf and mute, the Bible says:
"and looking up to heaven with a deep sigh, He said to him, 'Ephphatha!' that is, 'Be opened!' And his ears were opened, and the impediment of his tongue was removed, and he began speaking plainly," (Mark 7:34-35).
Perhaps our most relevant example, when Jesus was on the cross, we read:
"At the ninth hour Jesus cried out with a loud voice, 'Eloi, Eloi, lama sabachthani?' which is translated, 'My God, My God, why have You forsaken Me?' When some of the bystanders heard it, they began saying, “Behold, He is calling for Elijah," (Mark 15:34-35).
There are other examples, but this last instance is especially important for several reasons. The fact that the crowds misunderstood the Aramaic word "Eloi" to be the name "Elias" [Elijah in Greek] indicates that many in the crowd did not speak Aramaic. They had traveled from distant regions for Passover and did not know the local tongue. Since we know that Jesus addressed these crowds earlier, it increases the likelihood that Jesus spoke Greek in His public addresses to such crowds. Secondly, and even more important, if the words of Jesus are more reliable when they are in Aramaic, then these words of Jesus from the cross are among the most reliable ever reported. But these are words spoken during the crucifixion. Indeed, they quote from Psalm 22, applying that text prophetically to Jesus' death and coming resurrection. All of this affirms that Jesus did, in fact, die on the cross and that He died in fulfillment of prophecy in accordance with God's plan. All of this is antithetical to Islam, which claims that Jesus did not die on the cross at all. Thus, even in just the handful of Aramaic phrases we have from Jesus, we have a clear contradiction of Islamic teaching. If a Muslim assumes that words of Jesus reported in Aramaic are more reliable than words of Jesus reported in a language He did not speak (which would, again, certainly include Arabic) then the Muslim should abandon belief in the Quran and embrace the sacrificial death of Jesus in fulfillment of Old Testament prophecy. Thus, this fallacious argument, if taken seriously, actually leads to the opposite conclusion than the Muslim offering it would intend.
The truth is that all of the words of Jesus recorded in the New Testament are reliable regardless of whether they are written in the language that Jesus originally spoke them or whether they are divinely inspired translations. Nothing about the language of the New Testament invalidates its claims.