I will add my two cents on the matter. It is crucial to remember in all writings but doubly so with symbolic writings in the Bible, who the original hearers were. Rev tells us at the outset. It is a letter written to seven churches in Asia. The audience was largely, likely Jewish, and/or familiar with the Septuagint. Revelation may seem like a mystery and puzzle to us but John was not being given gibberish that would be meaningless to those it was addressed to. It was understandable to them because they knew from the OT what the symbols symbolized. It is necessary for us to gain our understanding of them from the same authoritative source. Their OT usage.
Good point, that. And it does, to me, anyway, reinforce
@David1701 's speculation that 'hand' and 'forehead' are, respectively, 'deeds' and 'thoughts'. But while I agree that it is symbolic language, I can't even say that "hand" and "forehead" there, ARE necessarily symbolic. Seems most likely, but my point is only that vehemence on meaning is out of place here.
There are many places in Scripture that I find not only the first meaning —what so many proudly proclaim as 'plain reading'— is called for, but layers upon layers of possible uses are also there. For example, 'types' are not only history, but foreshadowing. The rules of hermeneutics are common sense—they are not scripture, except where they are as such found IN scripture.
We all operate somewhere on a range between Scripture not being authoritative but the 'witness of the Holy Spirit' to my heart/mind being authoritative, to Scripture having all authority, even beyond my subjective notions that may or may not be a result of hints the Spirit seems to be giving me. We have one who says, "God made me say this, so why are you objecting?" and another who says, "I have studied this all my life, with intellectual honesty, and prayed urgently about it, so this is it!"
I say, "baugh!" to both extremes. When I hear them, my 'pure and unbiased thinking' almost wants to believe whatever they DON'T believe, regardless of what I believed before they posted! "I've had it up to here" with those who claim to be unbiased and pure in their attendance to "the Spirit's promptings" and those who claim to be unbiased and pure in their intellectual integrity.
When I read scripture earnestly, large swaths of it, searching for understanding, praying for wisdom, and I get a notion that seems too good to be true, I can't trust it, but must, (like Mary, lol) keep all these things and ponder them in my heart. For all I know, the Spirit may even be telling me what I need to hear at this juncture, to steer my thoughts one direction or the other, but is far from the whole story.