Gregory the Dialogist

And as a spirit passed before my face, the hair of my flesh stood up. But when the mind is suspended in contemplation, when, exceeding the narrow limits of the flesh, with all the power of her ken, she strains to find something of the freedom of interior security, she cannot for long rest standing above herself, because though the spirit carries her on high, yet the flesh sinks her down below by the yet remaining weight of her corruption. And hence it is added, And as a spirit passed before my face, the hair of my flesh stood up. …

Morals on the Book of Job, Book V ↗

Thomas Aquinas

As a consequence, he shows the cause of this fear when he says, "When a spirit glided past my face; the hairs on my flesh stood up." For it is reasonable that one with lesser power is awestruck in the presence of one with greater power. It is obvious that the power of the spirit is greater than the power of the flesh and so it is not surprising that the hair of the flesh stand up in the presence of the spirit as happens when one is overcome by sudden fear. …

Commentary on Job ↗