The word religion is extremely rare in the New Testament and the writings of mystics. The reason is simple. Those attitudes and practices to which we give the collective name of religion are themselves concerned with religion hardly at all. To be religious is to have one’s attention fixed on God and on one’s neighbour in relation to God. Therefore, almost by definition, a religious man, or a man when he is being religious, is not thinking about religion; he hasn’t the time. Religion is what we (or he himself at a later moment) call his activity from outside.
… C. S. Lewis, “Lilies that Fester”