John Piper on Rewards
Beware of commentators who divert attention from the plain meaning of these texts. What would you think for example, of the following typical comment on Luke 14:13-14 "The promise of reward for this kind of life is there as a fact. You do not live this way for the sake of reward. If you do you are not living this way but in the same old selfish way."
Is this true- that we are selfish and not loving if we are motivated by the promise of reward? If so, why did Jesus entice us by mentioning the reward, even giving it as the basis ("for") of our action? And what would this commentator say concerning Luke 12:33, where we are not told that reward will result from our giving alms, but we are told to actively seek to get the reward "Provide yourselves with purses!"?
So it is simply wrong to say that Jesus does not want us to pursue the reward he promises. He commands that we pursue it (Luke 12:33, 16:9). More than forty times in the Gospel of Luke there are promises of reward and threats of punishment connected with the commands of Jesus.
Desiring God, p.166
John Piper is not Free Grace. The chapter in this book on conversion is absolutely appalling. I think John Piper's teaching on Desiring God is rather unbalanced and I would not recommend it. Neverthelss these paragraphs are a rare gem and are possibly the best part of the whole book.