It's quite telling that this parable follows the parable of the ten virgins. Just as a teacher will explain an idea in different ways, the idea in the previous parable is being explained in an alternate way. The important takeaway is that a believer needs to maintain a surplus of faith because the task he will be asked to do may require that extra faith.
How does a believer acquire faith?
There is information in the text that faith is initiated by God. It doesn't mean that faith is a gift, given as a final product or resource, to help in accomplishing the task (as Wallace and Mounce confirm, in their interpretation of the Greek of Ephesians 2:8). Rather, the idea is that a process that generates faith is started, and grows, depending on affinity with God’s character.
God created a crisis in the desert by not making arrangements to supply food and water to Israel. Israel panics. So far, no harm, no foul. God saves from the crisis.
God asks Israel to overcome the Canaanites and take possession of the Land. This is the task mentioned, that requires a prior exercising and building up of faith.
Joshua remembers the great works God did in Egypt and in the wilderness. He puts it all together. God had promised that the world would be blessed through Abraham's descendants. This will happen if the world sees God on Israel's side and believes in the benefit it results in, of leaving selfish living and turning to follow God, which in turn will make them blessings to yet more people like Rahab. God's command to overcome the Canaanites is the way He will deliver the world from harmful selfish living.
Israel forgets the great works God did. This speaks a lot about her collective character, of trying to be God's sheep.
In not being God's sheep, not being clean, that the rest of Israel, that Judas, turned out to be, whatever faith they had from seeing the great works of the Son and the Father will be taken away. The world will see the negative model. Lacking strength and fortitude, the victims become easy pickings for Satan to lead into betrayal of God.
This is the opposite of the result of allowing mighty revelations to take root, and growing in faith, so that when called to manifest the privilege of being blessings, they have the benefit of having a faith reinforced by remembering God's great works, to follow through. Not allowing faith to be nurtured and nourished due to fear and cowardice and concern for interests of self leads to non fulfilment and experiencing of God's wrath. The negative example, the sight of those who fail, is a further incentive to the industrious believers to do even better.
The reference to reaping where seed is not sown, bread is not given, to dogs, yet still expecting the dogs to be fit, is because even the dogs eat of the crumbs that fall from the masters' table. Although Cornelius was not having the benefit of Covenant membership, he would still be expected to conform, as one who would be judged outside the Law.
Romans 2:12 NASB For all who have sinned without the Law will also perish without the Law, and all who have sinned under the Law will be judged by the Law