When churches began in the homes after Jesus' ascension, what would they teach from? We have the entire Word to speak on today but all they had was the OT. They had a few that had witnessed Christ & I'm sure they shared those things but they didn't have the letters or the gospels. So, what did they use?
It was common in the day for information to be carried and delivered verbally. Thus, in each church there was someone, often Paul, had started the church. This person would be responsible for teaching the basics to the group. Because this method was a regular method in the day they were very adept at it and would not find the telephone game being played out. Plus, by transmitting the information to several (or numerous) people at one time they then are able to hold each other accountable. The letters that Paul sent that we recognize as the Epistles were sent because he was absent and needed to communicate with them. Sometimes a false teacher had entered the picture and at other times they had simply gone off track.
John makes a statement that sort of highlights this personal communication method over the written in the following:
2Jn 1:12 NIV84 I have much to write to you, but I do not want to use paper and ink. Instead, I hope to visit you and talk with you face to face, so that our joy may be complete.