Both of these are unknown things with unknown qualities held in very real relation to each other, and that combination of the concrete (or as concrete as a metaphor can get) relation abstract concept holds the mind in thrall.
So much is left unsaid that the statement can come off as both self-evident to the point of not saying anything and abstruse to the point of not meaning anything, yet it rings true enough for me that it will get stuck in my head, and I’ll start diving down through these layers of meaning to try and pull it apart, to dig in the spaces between the letters of ‘holy’ and ‘fear’ for any extra meaning left behind by a long-dead author.
Layer after layer after layer, digging their way through levels of applicability and practicality, from that surface level interaction of what is holy and what is fear all the way down to that ineffable sense of the numinous that we can never explain and nonetheless still have within us.
-(( Probably worth reversing the order of subsections below ))