Causes becoming "numb"?

The context you give is written in almost archaic English. I doubt that its intended meaning would be properly understood today except perhaps those who think in a Christian religious context and firmly believe that God understands only Early Modern English.

Cause(s) is an awkward word to use in the context that you have given

You are trying to use it in the sense of someone who causes things

(OED)

Cause (n) 2. A person or other agent who brings about or occasions something, with or without intention. (Often in bad sense: one who occasions, or is to blame for mischief, misfortune, etc.)

1713 G. Berkeley Three Dialogues Hylas & Philonous ii. 80 God is the supreme and Universal Cause of all Things.

This use is rare. Usually "a cause" is understood as a political or philosophical principle or institution.

And you will see that numb is not quite right either.

Numb (adj.) b. In extended use: as if deprived of physical sensation or the power of movement; (in later use) (chiefly) spec. emotionally deadened, unresponsive, or spent, as the result of grief, shock, fear, etc. rare before 19th cent.

But this is not the common use of "numb" which usually means "lacking the ability to experience the sensation of touch."

"It's very cold out there! My fingers are numb."

Short answer: no, I don’t think so. The reason is not because a ‘cause’ couldn’t become ‘numb’ in a metaphorical sense (e.g. a revolution dying because the problem It was revolting against was removed) but because I don’t think you’re using the word ‘cause’ correctly. A cause cannot help a person in the manner you’re suggesting, and it isn’t clear to me what exactly your intended meaning was, but my answer still stands - in this context, no, that phrase does not work.