Ephesians 2:8-10
8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
9 Not of works, lest any man should boast.
10 For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them.
Ephesians 2:10 is occasionally used in response to the famous verses before it, essentially to say, "Really, Ephesians 2:8-9? Keep reading!", as if verse 10 somehow contradicts the plain message of verses 8 and 9 - that we are saved by faith, without works.
Does verse 10 teach that all believers will have some unknown level of good works, and therefore cannot be saved without them manifesting?
Virtually no professing Christian on the planet denies that a Christian "should" walk in good works, which is what the verse in question says. None that I'm aware of in the Free Grace camp, including myself, deny such a thing, and pretending that any of us do, either implicitly or explicitly, is slander.
What we deny is that a believer, who is saved by grace through faith, before they do a single good work - as the verses preceding the verse in question clearly teach - either must do good works to be saved, or will do some unknown, undefined quantity of good works if they are "really" saved. This verse teaches no such thing.
Rather, it's an exhortation to walk in good works, one of many such admonishments in Scripture:
Hebrews 10:24
24 And let us consider one another to provoke unto love and to good works:
Titus 3:8, 14
8 This is a faithful saying, and these things I will that thou affirm constantly, that they which have believed in God might be careful to maintain good works. These things are good and profitable unto men.
14 And let our's also learn to maintain good works for necessary uses, that they be not unfruitful.
As the above verses show, we have to be "provoked" to do good works, "be careful to maintain good works", and "learn to maintain good works", showing that this is not automatic, nor a guarantee.
Instead, the verse in question teaches much the same thing as the following verse:
Titus 2:14
14 Who gave himself for us, that he might redeem us from all iniquity, and purify unto himself a peculiar people, zealous of good works.
Both the above verse, and Ephesians 2:10, testify that the purpose of God in leaving us here on earth after Salvation, is so that we can be the light of the world, and others "may see our good works, and glorify our Father which is in heaven" (Matthew 5:16).
I want every single person reading this article to walk in the Spirit, and maintain good works. However, using the verse in question to teach that if you don't, to some unclear degree that I made up, it means you aren't saved, is a terrible mangling of Scripture.
Rather, this verse teaches that if you fail to walk in good works after Salvation, you are going against God's eternal purpose for your life here on earth, and are squandering an opportunity to glorify God, and earn eternal rewards for doing so (1 Corinthians 3:11-15).