I agree that he doesn't understand, and you'll see that in my responses to him. Yet, "obey the commandments" is actually what Jesus taught. The whole controversy is around salvation cause and effect. Reformed theology teaches that obeying the commandments (namely to love one's neighbor) is the effect of salvation, but the Remonstrants (in conjunction with the RCC) teach that obeying the commandments (in addition to faith) is the cause of salvation.
Paul taught that we are justified by faith alone, which is what the reformers taught, but they had to add to the statement "but not by a faith that is alone," because of those people who confused the definition of the faith that justifies. It's no different than the controversies of the 1st Century that prompted NT writings like James and Galatians. James wrote "faith without works is dead," because of people who were misusing the term "faith" and claiming they were Christians although they had no commitment (or possibly intention) to obey Christ's commands.
Isn't it true that "saving faith" as many in Reformed Theology put it, actually does include acknowledging Jesus as Lord, and being submissive to His will? So then, when Jesus (and the NT writers) command people to do right, to obey the 10 commandments, to be gracious to others, etc., aren't they trying to motivate people to exercising genuine faith in Christ? When Jesus commanded "love your neighbor," isn't it implied that one who has genuine faith in Christ can do so (and wants to do so) because they have the Holy Spirit, as John teaches in 1 Jn. 3:9?
We are saved by grace through faith, which is all (including faith) the gift of God. Grace is the enablement by God to believe the gospel and live according to Christ's commands, is it not?