The parable In Sunday’s Gospel seems a little bit “off” as Jesus appears to encourage dishonesty. However as with 
the parable of the Persistent Widow (Luke 18:1ff) Jesus is comparing some quality in this evil world with a similar but vastly superior quality in God’s Kingdom. The lesser is compared to the greater, thus magnifying the greatness of the greater.
The dishonest steward in the parable made friends with his master’s debtors by changing the books and thus allowing the debtors to have their bills reduced. He hoped these new “friends” would give him a job after his master released him. Strangely, the master commends something about the dishonest steward. Note well that the master did not commend the steward for dishonesty but for his shrewdness: “The master commended the dishonest manager for his shrewdness…” (v. 8a)
This is one of the key points of the parable: shrewdness. Thus Jesus makes the application: “…the sons of this world are more shrewd in dealing with their own generation than the sons of light.” (8b) The sons of light are those who have been brought to faith in Christ. Jesus is here encouraging these sons of light to be shrewd in their proclamation of the Gospel. How? Use the money and things of this world to get the Gospel out.
Jesus explains: “I tell you, make friends for yourselves by means of unrighteous wealth, so that when it fails they may receive you into the eternal dwellings.” (v. 9) Indeed we as Christians can and should use “unrighteous wealth” to “make friends”. Money/wealth, which is used in this world for all manner of unrighteousness and which has caused all kinds of evil as people lust for it, is nonetheless to be used for the work of Christ’s Church. Thus appropriately the Church collects and uses money and it builds nice buildings and it buys food and clothing for the poor. This “investment” of unrighteous mammon has as its “shrewd” goal that the Word of Christ be shared and people be brought into God’s family—made “friends” in Christ. The “friends” God makes in the church are not merely buddies or chums but they are friends in Christ, they are fellow believers, fellow heirs of heaven. Such “friends” have been told, “Take your bill that lists your sins, that shows all of your guilt, that even exposes your disease of original sin, and write that you owe nothing because Christ has paid for it all on the cross.”
Such friends in Christ are then not mere earthly acquaintances, they are people eternally joined in Christ. Our earthly wealth—unrighteous mammon—will indeed fail us in this life, for we will all enter the grave. How joyful it will be when we encounter in heaven people on whose behalf we have shrewdly invested our “unrighteous wealth” so they could hear the Word of Christ and believe. Yes, they will align with our joy and receive us into the eternal dwellings.