No. Not all intellectual substances are united to bodies because whenever we find something imperfect in any genus we must presuppose something perfect in that genus; therefore in the intellectual nature there are some perfectly intellectual substances, which do not need to acquire knowledge from sensible things.
It was the opinion of some that every being is a body; and consequently some seem to have thought that there were no incorporeal substances existing except as united to bodies; so much so that some even held that God was the soul of the world, as Augustine tells us (De Civ. Dei vii).
As this is contrary to Catholic Faith, which asserts that God is exalted above all things, according to Ps. 8:2: "Thy magnificence is exalted beyond the heavens"; Origen, while refusing to say such a thing of God, followed the above opinion of others regarding the other substances; being deceived here as he was also in many other points, by following the opinions of the ancient philosophers.
Bernard's expression can be explained, that the created spirit needs some bodily instrument, which is not naturally united to it, but assumed for some purpose, as will be explained (Q51 A2).
Augustine speaks, not as asserting the fact, but merely using the opinion of the Platonists, who maintained that there are some aerial animals, which they termed demons.