A Prologue to Love is a book by Taylor Caldwell. Seneca is quoted in the book. I'm not sure of the source of the quote by Seneca.

I'm not sure what you mean by "Quietism." I know it as the view that philosophy is therapeutic or remedial, and has nothing substantive or positive to contribute. I tend to think of modern philosophy in that way. I think some ancient philosophy was positive in the sense that it provided good practical wisdom regarding how to live, and even spiritual guidance, though.

I'm not sure what you mean by "Quietism." — Ciceronianus

AT the very least, it seems to me to be a stance or position to assume towards certain questions in life. Such as questions about God or existential concerns.

I would assume you are well acquainted with why these questions bother some, whilst Quietism would seem to profess an attitude of (indifference?) if non-care towards them; but, not based on emotive reasonings; however based on rational grounds.

The quote from (allegedly) Seneca was for some reason written by my father on the preface before he gave me his own Bible to read or rather disregard as I came to feel that profound quote towards my-self.

God is too inscrutable to understand or even reason with.

However, I do not seek divine revelation; but, rather choose to believe in what I have come to understand myself. Just as a passing note, what happened to Job was too gratuitous to understand.

.... only a prologue to love beyond the grave, where all is understood and all forgiven. — Seneca

Because "beyond the grave" all is forgotten.

I would assume you are well acquainted with why these questions bother some, whilst Quietism would seem to profess an attitude of (indifference?) if non-care towards them; but, not based on emotive reasonings; however based on rational grounds. — Shawn

I'm aware they bother some, and have an opinion why they do. Quietism, I think, simply recognizes that philosophers haven't and likely will never provide an answer to those questions, if they properly can be called "questions." That doesn't necessarily mean Quietists are indifferent to them, but they understand, e.g., that language has limitations, and some things must be shown as Wittgenstein said.

I'm not sure what you mean by "Quietism." — Ciceronianus

Quietism (Latin quies, quietus, passivity) in the broadest sense is the doctrine which declares that man's highest perfection consists in a sort of psychical self-annihilation and a consequent absorption of the soul into the Divine Essence even during the present life. In the state of "quietude" the mind is wholly inactive; it no longer thinks or wills on its own account, but remains passive while God acts within it. Quietism is thus generally speaking a sort of false or exaggerated mysticism, which under the guise of the loftiest spirituality contains erroneous notions which, if consistently followed, would prove fatal to morality. It is fostered by Pantheism and similar theories, and it involves peculiar notions concerning the Divine cooperation in human acts.

https://www.newadvent.org/cathen/12608c.htm

Also, search Garrigou-Lagrange's Three ages of the interior life for "quietism" and "acedia". He classifies quietism as spiritual sloth, most dangerous to a person's spiritual progress.

Quietism sounds like the Christian/Catholic response to meditation. Only the latter is generally not explicitly about God, the meditator "yields" the ego's desires to something greater, all the same. God, after all, is a terrible nuisance in metaphysics, and it closes doors, often, because the body of religion around it is dogmatic. I'll take the holiness and put aside the metaphysics. This at least purifies the concept to something immanent and unquestioned, but of course, the term 'holy' is left self sustaining.