What an ironical statement! On first read it would sound like you agree that a person is saved by grace through faith apart from works since you state that work done out of obligation...is not salvific. Yet I know quite well from past posts that you adhere to your religious doctrine that faith and works are necessary for salvation. What, then, do you mean by "obligation"?
We "Protestants" have been saying all along that the good works God has prepared for us to do are because we are saved and not in order to be saved. When we are genuinely "born from above", we are new creatures, there is a new nature that desires to please God, that yearns to obey him out of love and gratitude and NOT obligation. The Reformation happened for many reasons but one of the chief ones was the Church had forsaken the primal doctrine of "saved by grace through faith alone".
I highly doubt this has just been a case of mistaken semantical misunderstanding all these centuries!
For example, a Jewish law said that one is obligated to circumcise his children. That is a work of law, in this case Hebrew law, that is not salvific for that very reason, and St. Paul wrote two epistles -- to Romans the to the Galatians explaining that.
We "Protestants" have been saying all along that the good works God has prepared for us to do are because we are saved and not in order to be saved
Yes, and that is precisely the counterscriptural heresy, as we've seen from several verses. We are nto saved till we are judged, and we have to do works of love if we want to be saved (Mt 5-7. Mt 25, Rm 2:6-10, Ja. 2, Eph. 2:10, Phil. 2:12-13).