How is Sin Against God?
Tolkien himself once approved the interpretation of the roles of Aragorn, Gandalf, and Frodo as representing the three-fold office of Christ as king, prophet, and priest (Clyde Kilby, Tolkien & The Silmarillion, ch. 4). Aragorn is the king who rules and brings peace to the land. Gandalf is the wise prophet who counsels and encourages others. Frodo is a priestly figure who, like Christ, sacrifices himself (is both priest and victim) for the sake of others.
What has been missed is that Tolkien subtlety shows that there are more spiritual attacks against the priest figure than any other character. Frodo gets attacked, and seemingly random attacks land on him, more than any other member of the Fellowship. There are four key places this shows up in The Lord of the Rings.
First, as the Fellowship is entering the abandoned dwarven mines of Moria, a strange and hidden creature attacks the Fellowship. It grabs Frodo with a tentacle and tries to drag Frodo away. Sam saves Frodo by hacking at the tentacle and the Fellowship dashes inside the mines. The first and only member of the Fellowship which the creature had been able to attack was Frodo. Gandalf notices this oddity but does not point it out to the rest of the Fellowship.
Second, when the Fellowship is in Moria, at the tomb of Balin, they are attacked by a band of orcs with a cave troll. They fight off the first attack and turn to flee down another passage. But as the Fellowship turns to leave, a single orc enters the chamber and attacks Frodo:
But even as they retreated, and before Pippin and Merry had reached the stair outside, a huge orc-chieftain, almost man-high, clad in black mail from head to foot, leaped into the chamber; behind him his followers clustered in the doorway. His broad flat face was swart, his eyes were like coals, and his tongue was red; he wielded a great spear. With a thrust of his huge hide shield he turned Boromir’s sword and bore him backwards, throwing him to the ground. Diving under Aragorn’s blow with the speed of a striking snake he charged into the Company and thrust with his spear straight at Frodo. The blow caught him on the right side, and Frodo was hurled against the wall and pinned (Tolkien, The Lord of the Rings, II.5).
This lone orc runs past Boromir and Aragorn, dodging their attacks, just to stab Frodo. A very odd thing for a lone orc to do. It seems like a suicide mission for him to ignore the main warriors and specifically target a small, not very dangerous, hobbit.
Third, as the Fellowship leaves Moria, they must pass over the tiny Bridge of Khazad-dum. As they approach the bridge and cross it, the orcs shoot arrows at them from a great distance. Thus, most arrows fall harmlessly. Yet, one strikes Frodo. He would have been killed, if he were not wearing the mithril coat of armor which protected him.
Fourth and finally, after leaving the forest of Lothlorien the Fellowship travel down the river Anduin in small boats (canoes) that the lady Galadriel gave to them. They eventually float into a section of the river that is dangerous, with rapids and orcs on one side of the river who might shoot at them. As they float by at night, the rapids drive them too close to the orc-infested side of the river and the orcs shoot arrows at the Fellowship wildly during the night. Most of the arrows miss, but once again one hits Frodo. Once again, he is only saved by his hidden coat of mithril.
These four episodes are odd. In the first two, Frodo is the one whom the enemy attacks, seemingly at random but also with a clear intent to attack him individually. In the second two, Frodo is the only one whom arrows hit. These unfortunate events for Frodo signal to the reader that the one in the priestly role, the one bearing the burden on behalf of others, should expect more danger and trials than others. He is, in a way, the true chief enemy of Sauron and the forces of evil, even if Aragorn or Gandalf is more powerful.
In the real world, this warns us that priests should expect more spiritual attacks than the ordinary Christian. The demons hate priests especially and will target them more. Priests must be prepared for these attacks with their own form of hidden mithril armor, a spiritual protection of a deep spiritual life full of the sacraments. But also the faithful can help protect the priests like the Fellowship protects Frodo, by their prayers and sacrifices done for the priests.