Today Paul’s concern for the Galatians comes through (along with some personal frustration) and we see just how strongly he felt for them in vv.8-11.
Formerly when you did not know God, you were enslaved to beings that by nature are not gods at all. But now that you have come to know God (or rather to be known by God), how can you turn back again to the weak and worthless basic forces? Do you want to be enslaved to them all over again? You are observing religious days and months and seasons and years. I fear for you that my work for you may have been in vain. I beg you, brothers and sisters, become like me, because I have become like you. You have done me no wrong!
Again Paul is reminding them that before they believed, they were enslaved to beings that by nature are not gods at all. This could have included a vast and varied plethora of pagan gods (Acts 14.11-13, for example). At that point in their lives, the Galatians did not know God nor were they living like they were known by God (v.9). Formerly they were not saved and justified and they were certainly not living as if they were saved and justified. Paul is dismayed that now their salvation is before them, they are turning back again to the weak and worthless basic forces. He asks them if they wish to be enslaved to them all over again?
Nothing they can add to their faith will increase their standing before God (v.10), and Paul is seriously concerned that his work among them may have been in vain. He is worried that he has worked hard to explain and expound the Good News only for them to view it as something that needs to be added to with a pinch of paganism or a dash of special-day observance.
For you and for me, Galatians 4.8-11 can be seen as a heartfelt plea from a pastorally-hearted teacher of truth to his people: once you have started down this road of living by faith alone please, please, don’t turn back, don’t become enslaved all over again, don’t try and add your own works to the finished work of Jesus in order to bolster your standing before God, and please spare a thought for how this weighs on those who have taught you about the truth of Jesus.