Charles Ellicott Commentary Galatians 6:13

"For not even they who receive circumcision do themselves keep the law; but they desire to have you circumcised, that they may glory in your flesh." — Galatians 6:13 (ASV)

Their insincerity is shown by the fact that they are not really careful to observe the Law. What they do is only to serve as a pretext, that they may be able to point to your mutilated flesh as the visible sign of their success in making converts.

They themselves who are circumcised.—The expression in the Greek includes, not only those who were circumcised themselves, but also those who advocate for circumcising others.

Glory in your flesh.—Boast about having this rite performed on your bodies.