Luke 15:10 Likewise, I say to you, there is joy in the presence of the angels of God over one sinner who repents.
The interpretation of this verse suggests that heaven celebrates when a sinner repents, but the beginning of the chapter implies something different. The focus of the first two parables, one about a lost sheep and the other about a lost coin, is on the person who finds them, not on what is found. One actively searches for the lost sheep, while the other searches for the lost coin, and once they find what they find what was lost, they call their neighbors to rejoice with them. But take note of this, this rejoicing is not because of the coin or the sheep, but because they have found what was lost.
Therefore, Luke 15:10 informs us that heaven rejoices over God when they witness every time He finds (saves) lost sinners. That is to say, the rejoicing is over the FINDER not the FOUND. We are the ones who benefit from what He has done, and He deserves all the credit.