In Ephesians we find that light (religious truth) is described as very powerful as it is able to make dead things living just by shining on them.

But when anything is exposed by the light, it becomes visible, for anything that becomes visible is light. Therefore it says,
“Awake, O sleeper,
and arise from the dead,
and Christ will shine on you.”

(Ephesians 5:13-14, ESV)

However, this is no direct quote of any biblical passage, so I imagine Paul simply puts it in his own words to apply it to the context. But what is ‘it’; what scripture is he paraphrasing here which fully suits the context? Why is it an appropriate verse to quote in this context?