“Religion” is typically considered as a “belief system” or a “structure of beliefs and practices concerning the divine.” It’s a recent development in the meaning of the word, and it would have been foreign to, say, Aquinas, for whom religion was a virtue.
A virtue is the perfection of a power of the soul, or, in modern parlance, an excellenceof the human person. We see a height of humanity in courageous actions, a greatness we are all capable of. We admire courage, not as something for just this or that person, but as something every human being can and ought to aspire to. Virtue, then, is not the addition of some pleasing quality, slapped on like a sticker on the surface of this or that person. Virtue is the perfection of those powers and capacities every person really does have, our indwelling capacities for courage, patience, justice — and religion.