The debates surrounding the nature of sanctification are never ending in both Lutheran and Reformed circles. There has been quite a bit of controversy, as of late, surrounding some particular phraseology utilized by John Piper in his forward to Thomas Schreiner’s recent volume on justification. In this forward, Piper writes:
“The stunning Christian answer is: sola fide—faith alone. But be sure you hear this carefully and precisely: He says right with God by faith alone, not attain heaven by faith alone. There are other conditions for attaining heaven, but no others for entering a right relationship to God. In fact, one must already be in a right relationship with God by faith alone in order to meet the other conditions.” 
In this text, Piper distinguishes between justification and attaining heaven. Piper argues that faith alone is necessary for one to be initially justified, but that there are other necessary conditions following justification in order for one to receive entrance into eschatological glory. These conditions are, of course, good works following true faith. A number of Reformed writers have come to Piper’s defense. Mark Jones, for example, wrote a defense at Reformation 21 arguing that Piper’s formulation does not differ in any significant way from the historic Reformed tradition. He cites Turretin as saying:
This very thing is no less expressly delivered concerning future glory. For since good works have the relation of the means to the end (Jn. 3:5, 16; Mt. 5:8); of the ‘way’ to the goal (Eph. 2:10; Phil 3:14); of the ‘sowing’ to the harvest (Gal. 6:7,8)…of labor to the reward (Mt. 20:1); of the ‘contest’ to the crown (2 Tim. 2:5; 4:8), everyone sees that there is the highest and an indispensable necessity of good works for obtaining glory. It is so great that it cannot be reached without them (Heb. 12:14; Rev. 21:27). 
At the heart of this discussion is a differentiation that is made between present justification and reception into eschatological glory. This allows some writers to argue that salvation is by faith alone in one sense (justification), and by both faith and sanctification in another (entrance into heaven). This is similar to distinctions made by the New Perspective on Paul, as well as some writers within the Federal Vision who distinguish between two senses of justification: present, and eschatological. There are two primary concerns I have with this type of language. First, this tears apart justification in the present and one’s eschatological vindication. These are not two separate events, but justification is one’s eschatological vindication received proleptically. Thus, if justification is received sola fide, then so is any eschatological soteriological blessing. Yes, it is true that all Christians who possess faith will also perform good works, and yes it is true that these works will evidence the reality of one’s faith at the final judgment. It is also true that no one is justified without also beginning a life of sanctification, and that there are heavenly rewards for good deeds performed. However, the necessity of good works, and the inevitability of good works do not make them a condition for entering eternal life. In their zeal to fight against antinomianism, it is my fear that these writers are compromising the full and free nature of salvation.
Second, I worry about this language pastorally. Sure, theologians can make nuanced distinctions between justification and one’s “attaining heaven.” We can speak of different kinds of necessity, calling good works a “consequent necessity” for salvation, etc. But, are these distinctions valuable for the average congregant? If I preach and use the phrase “good works are necessary for salvation,” how is this going to be understood by my congregation? Unfortunately, this ultimately places the Christian in the same dilemma as the medieval church. Yes, I can reject the language of merit, and talk about salvation by grace, but isn’t one ultimately pointed back to their own good works for assurance of salvation? What good is it for justification in the past to be received sola fide, but future salvation to be of both faith and works? I understand that theologically and linguistically this differs from the Medieval Roman system, but I wonder if it really does pastorally?
The authors of the Formula of Concord addressed this exact issue, and in doing so, offer some extremely valuable commentary:
22] But here we must be well on our guard lest works are drawn and mingled into the article of justification and salvation. Therefore the propositions are justly rejected, that to believers good works are necessary for salvation, so that it is impossible to be saved without good works. For they are directly contrary to the doctrine de particulis exclusivis in articulo iustificationis et salvationis (concerning the exclusive particles in the article of justification and salvation), that is, they conflict with the words by which St. Paul has entirely excluded our works and merits from the article of justification and salvation, and ascribed everything to the grace of God and the merit of Christ alone, as explained in the preceding article.23] Again, they [these propositions concerning the necessity of good works for salvation] take from afflicted, troubled consciences the comfort of the Gospel, give occasion for doubt, are in many ways dangerous, strengthen presumption in one’s own righteousness and confidence in one’s own works; besides, they are accepted by the Papists, and in their interest adduced against the pure doctrine of the alone-saving faith. 24] Moreover, they are contrary to the form of sound words, as it is written that blessedness is only of the man unto whom God imputeth righteousness without works, Rom. 4:6. Likewise, in the Sixth Article of the Augsburg Confession it is written that we are saved without works, by faith alone. 
I know that John Piper, Mark Jones, Kevin DeYoung, and others who have utilized this terminology are not intentionally compromising the doctrine of justification by faith, and they surely would reject the language of Rome in this regard. I fear, however, that this theology is dangerous pastorally, especially to burdened consciences who need to be pointed to the unconditional promises of God as given in his means of grace.
 – See more at: http://www.reformation21.org/blog/2015/09/in-defense-of-piper.php#sthash.h8RBITcZ.dpuf