If we're going to talk about what's going on when Israel doesn't take any spoils from their defeat of the Persians at Purim (the book of Esther), then we should start by looking at Israel's relationship to plunder throughout her history.
And essentially, there are two narratives here.
The first narrative is that sometimes, we take no plunder. We take no plunder because the peoples we are coming up against are simply too wicked and their practices and possessions are so corrupt that we could not possibly bring them into our own culture without corrupting ourselves.
When this is the case, God's people have been instructed to simply burn everything. Burn it all. Destroy it thoroughly. Make sure that there is not one recognizable atom left on top of another so that absolutely nothing impure can possibly make its way into Israel's camp.
This was the sin of Achan. It's not just that he took something when God had instructed them not to take anything. It's that what he took was so thoroughly impure that he brought an uncleanness into Israel's camp by the very item itself, not to mention his own sin of disobedience.
This was not some kind of test that God was running of His people. "Will they, or won't they, destroy what I tell them to destroy?" We have to get out of that kind of mindset of God because that's not the kind of God that He is. This was an act of kindness from God, in that He knew how corrupt the spoils were from these towns and these peoples, and He knew He had to keep them away from His own people, lest their hearts start to wander toward impure things.
So sometimes, we take no spoil, and when we don't, we burn everything.
The second narrative that we have with the spoil is that sometimes, we take what is pure or what can be purified. This is where we are when God talks about keeping the livestock, for example, and the jewels and any woman who has not been with a man.
Here, we're looking at things that can be passed through fire...or don't have to be. We're looking at things that will not be burned up easily, but will be purified by heat. We're looking at things like livestock that can be an aroma pleasing to the Lord, that are not defiled, per se, by their peoples' living and thus are well to become a sacrifice. And, of course, we're talking about virgins - young girls who have not been corrupted by their culture yet, who have not been defiled, who have not been responsible for impure rituals of cultic worship.
In these cases, God lets His people take what is clean or what can be clean. These things become, then, reclaimed in a sense. They are an example of the resurrection, of the kind of redemption that can happen when God's promises are being fulfilled. These spoils are a reminder of what God is doing in all of us.
Imagine the jewelry from Egypt that becomes tarnished over the years by wandering in the wilderness for so long, but then one day, is purified and cleansed and becomes bright again and it no longer tells the story of Egypt, but of Exodus. That's what we're talking about. That's what God does with the spoils when He lets us take them.
So sometimes, we take spoil, and when we do, we tell a story of reformation.
These are the two primary relationships that Israel had with the plunder of the nations she came up against. But...it is not the story of Purim. Purim was entirely different. How? And...why?