God is a Spirit

Of course we know this most truly and certainly because it is the teaching of Scripture: "God is spirit, and they who worship him must worship in spirit and in truth" (John 4:24 CCD). But this is a truth that may also be arrived at by way of reason.

It is absolutely true that God is not a body; and this can be shown in three ways.

First, because no body is in motion unless it be put in motion, as is evident from induction. Now it has been already proved [ST I Q2 A3], that God is the First Mover, and is Himself unmoved. Therefore it is clear that God is not a body.

Secondly, because the first being must of necessity be in act, and in no way in potentiality. For although in any single thing that passes from potentiality to actuality, the potentiality is prior in time to the actuality; nevertheless, absolutely speaking, actuality is prior to potentiality; for whatever is in potentiality can be reduced into actuality only by some being in actuality. Now it has been already proved that God is the First Being. It is therefore impossible that in God there should be any potentiality. But every body is in potentiality because the continuous, as such, is divisible to infinity; it is therefore impossible that God should be a body.

Thirdly, because God is the most noble of beings. Now it is impossible for a body to be the most noble of beings; for a body must be either animate or inanimate; and an animate body is manifestly nobler than any inanimate body. But an animate body is not animate precisely as body; otherwise all bodies would be animate. Therefore its animation depends upon some other thing, as our body depends for its animation on the soul. Hence that by which a body becomes animated must be nobler than the body. Therefore it is impossible that God should be a body (ST I Q3 A1).

From this we see that it is not merely blasphemous and profane to say that God is or has a body. It is irrational.