Galatians 5:3-4
And I testify again to every man who becomes circumcised that he is a debtor to keep the whole law. You have become estranged from Christ, you who attempt to be justified by law; you have fallen from grace.

The Book of Galatians is about following the Mosaic Law as an addition to one’s salvation – especially the act of circumcision.
However, that is enough. To follow the Law in one point means you need to follow the Law in all points, that is, you must follow the whole Law. You do not get to pick and choose what you do or do not want to follow.
Christ fulfilled the Law for you.
To insist in adherence to the Law after salvation is to estrange yourself from Christ and depart from grace.
A reminder that you are saved by grace through faith and not the Law and when you begin following the Law, you fall [away] from grace.