I believe nearly all, if not all of the sentences written around the game are quotes from the Bible, and from as far as I can tell, many are from the fifth book of the New Testament, the Acts of the Apostles, usually shortened to "Acts."
In "The Caves," there is a quote from Isaiah 17:1 (King James version):
Behold, Damascus is taken away from being a city, and it shall be a ruinous heap.
The quotes that appear near the end of the game are specifically referring to Paul the Apostle's conversion (who was known as "Saul" before he converted) . They seem to be taken from different translations. In regards to the shift from third to first person, that is how his conversion was told in the Bible itself (Acts 9 was in third person, Acts 22 was Paul giving a speech about his experience, and is thus in first person).
The sentence written in the small shack on the way up to the cliffside is from Acts 9:3-4 (New Living Translation):
Acts 9:3 -
...a light from heaven suddenly shone down around him.
Acts 9:4 -
He fell to the ground...
The writing on the cliffside near the end is from Acts 9 and 22 (King James version) as follows:
Acts 9:9 -
And he was three days without sight, and neither did eat nor drink.
Acts 22:6 -
And it came to pass, that, as I made my journey, and was come nigh unto Damascus about noon, suddenly there shone from heaven a great light round about me.
Acts 22:11 -
And when I could not see for the glory of that light, being led by the hand of them that were with me, I came into Damascus.
Before you get to this point in the game, you see shortened versions of these excerpts, like "I came into Damascus" and "neither did eat nor drink," which is what was written on the side of the large boat you saw.
Also, 'ACTS 22:0' is written on one of the rocks by the sunken boats near the beginning of the game.
