What is a Gospel?
The question might sound strange. Everyone knows that we have four Gospels. But when we speak about the four Gospels, we do not use the word in its original meaning. Originally “gospel” meant the good message about Jesus Christ. It is the message from him and about him. Thus, it is not a question about a writing, but of a joyous news, a message from God about something that happened for our sake. In the New Testament, “evangelist” does not mean an author of a book of the Bible, but a circuit-riding proclaimer who comes with the news of Jesus. Therefore, the superscription to the “Gospels” reads, for example, The Gospel According to Matthew. There is only one Gospel. But this one Gospel is brought to us by four different witnesses. Their writings have then come to be called “Gospels.” But this use of the word is not found in the early church before the year 150.
How Have We Received The Gospels?
Many propose that one really cannot know anything certain about Jesus. He, of course, did not leave any writings. Of our Gospels, the one that is regarded as the oldest is Mark, which was written approximately 35 years after Jesus’ death. Matthew and Luke are usually dated ten or twenty years later. What then does one know about Jesus?
At the beginning of the twentieth century, one gladly proposed that Jesus was a folk prophet, a religious genius, who wandered about and spoke inspiringly and with a warm heart concerning God’s kingdom and who, in the end, gathered a group of admirers and friends. When suddenly the Master was gone, his followers attempted to remember what he had said. They spoke about him to others. Thus, there arose a collection of more or less occasional short stories about what Jesus said and did. They were spread by word of mouth, they grew, and they evolved just as rumors do when they are spread. They were shaped according to new needs to answer new questions. They were expanded with prophetic visions and revelations that some charismatics had, and which now pass as historical events. When the first evangelists sat down to write, there was not much to hold to with certainty. As a comparison, one can think of what it would be like for one of us to write a little book about our grandfather when we only had the memories of relatives to go on, and not what we ourselves could remember or had heard said.
This approach is a completely unrealistic way of looking at things. It ignores the reality of where Jesus lived and the environment in which the Gospels came into existence. Today, we can get a particularly good picture of the process, thanks in no small part to Swedish research in the last fifty years. 
We know that Jesus was called a rabbi by his contemporaries. This already says something particular about him. No one would be called “Preacher” in Sweden if he did not preach. If someone was called “Rabbi” in Palestine, it was because he was a teacher who instructed in the rabbinical manner.
A rabbi had a circle of disciples around him, whom he regularly instructed. His instruction went on to explain and build on what his disciples had learned. A Jewish boy (of those who had the privilege to go to school) would, at the age of 5 to 7 years, already begin the process of learning to read the scriptures in Hebrew and eventually would learn a lot of things. After some years, he was mature enough for a higher level where the Scriptures were laid out and commented on, always through an oral presentation that one would commit to memory and learn to repeat word for word. Finally, one could be a rabbi’s disciple. With the rabbi, there occurred conversation and discussions, but the content was always summarized in a few concentrated sentences that were once again taught. It was not normal for a student to repeat what the teacher said in words that were not taught and memorized. A student would do it “with the teacher’s word,” as the expression was heard. It is hard for us to imagine what a role memory skill played at that time. We are accustomed to acquiring our knowledge from books, and trusting in reference works when we need something. Books were rare among Jews.
The Holy Scriptures were certainly written down, and they would have always been read from scrolls, no matter how well one could recite them from memory. But all the explanations, commentary, and applications were kept from memory. People were completely opposed to writing them down. Instead, they took up the enormous job of teaching as many people as possible to repeat them correctly. Such knowledge was called Mishnah, which literally means repetition in Hebrew.
Thus, that Jesus could be conceived of as a rabbi by contemporaries means that from the great mass of more or less casual listeners; he also had a circle of disciples who he instructed privately and that this instruction was summarized in keywords and short phrases that were learned by heart before going further.
The Gospels confirm that Jesus really did gather a circle of disciples around him, whom he then instructed separately.
But it was not only what a rabbi said that his disciples put to memory. It also belonged to the matter that he instructed by example. The disciples would take notice of what he did and then convey the knowledge to others. When one then carried it further, it would happen with the same words that one heard the original disciples use.
The Gospels confirm that Jesus really did gather a circle of disciples around him, whom he then instructed separately. They could ask questions just like a rabbi’s disciples, and they received authoritative answers. They gave attention to his manner of operation and put it to memory. From that, one could assume that they were able to remember summaries of what the Master said. Among the Jews, to “instruct” meant first and foremost to inculcate something that the students would memorize and then give them knowledge which they carried in memory.
Thus, after the death of Jesus, the apostles did not stand before the difficult task of trying to remember what he said. Instead, they were bearers and stewards of all that which he had taught them. What they themselves were able to formulate were the stories of his deeds. These stories quickly received a firm and established form that was then circulated among new people.
Paul’s letters confirm that this is what happened. The oldest among them were written barely 20 years after the death of Jesus. At this time, there was a particular, rather clearly delimited knowledge of Jesus with his words and deeds that the apostles managed and conveyed. Paul had apparently been familiar with it and felt himself obligated to circulate it to all his congregations. When he answers questions from the congregations, he indicates whether he has a word from the Lord (meaning Jesus Christ) to reference or if he, in the spirit of his commission as an apostle, gives a regulation or a rule. This collected treasure of knowledge about Jesus is called parádosis in the Greek of the New Testament, a word that is hard to translate but means “something handed over” (hand down). These terms mean that one “receives” or “announces” (or rather: “passes on” or “provides”) these entrusted goods. It is an expression that has its direct corollary among the Jews, where the exposition of Scripture in this manner was orally received and relayed.
That Jesus did not leave one written line is nothing remarkable. None of the great rabbis left any written record, but their teachings were faithfully preserved until, approximately two centuries later, they began to be recorded. Within Judaism, one had—and this is true elsewhere in the world of antiquity—a penchant for the spoken word, that which was heard with a living voice, and regarded it as superior to the written word. Therefore, the rabbis opposed to recording the orally received Scripture lesson in writing. There are many hints among the early church fathers that even within Christendom, people regarded it to be a mistake, a misstep from the old, good order when men began to set to paper what had before been a treasure preserved in the hearts and memories of people.
That Jesus did not leave one written line is nothing remarkable.
When the first evangelist—in all probability, Mark—sat down to write a Gospel, he did not need to search for his material. It was already finished. What he wrote down was such as he himself had heard time after time during the divine service, such as he and many others could recite by heart. What the evangelists did was, primarily, to order and join this material together. Naturally, on a series of points, one can ask to what degree they put their own stamp on the text. These are questions that are taken up in the commentary. Even these many questions that touch upon the fourth Gospel must have their own treatment. Here it will only be emphasized that the evangelists are not authors in our sense of the word; neither are they historians that look for facts about the past in old documents or by interviewing the eyewitnesses that are still living. They are recorders of a firmly formed tradition that they learned and became familiar with over the years in the church’s divine service and under her instruction.
This does not exclude that they could have had access to written notes. There is every reason to believe that such things occurred. There is a rather strange circumstance that indicates this was usual. It is a fact that books (such as we are accustomed to using, ones stapled together in the spine with pages, as opposed to long scrolls) occur earlier in the church than otherwise in the world of antiquity. It was common already in the second century, and these were used precisely for the Gospels and other New Testament writings. It has been assumed that this was because the first written recordings of Jesus’ words and deeds were notes in notebooks and that because of this, people had become accustomed to reading them in stapled “books” and not scrolls.