How did they know?

When Jesus gave the Sermon on the Mount, the people asked Him ,"How should we pray?"
His answer was The Lord's Prayer. Our Father which art in Heaven, Hallowed be thy name and so on.
But, how did the people remember what He said?
Did they have someone with a stylus and parchment nearby to catch the words He spoke?
Or did they go amongst the populace afterwards asking people to recall what they had heard until they had the whole thing down in writing so they wouldn't forget?
There is no explanation in the Bible of how the words Jesus spoke were recorded.
It is all just taken for granted that they were what He said.
But , how?
I, too believe in the words of The Lord's Prayer as coming from Christ Himself, but how were they first written down?
By whom?
This question can be applied to many episodes in the Bible.

The answer to it would provide many a delicious story about Biblical characters.
A whole off shoot of different stories about the life and times of Jesus, our Lord and Saviour.

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