Regarding the law as a Divine ordinance for our direction, they consider themselves prepared and fitted by conversion to take up the fulfilment of the law as a natural duty. They know not that, in the New Covenant, the law written in the heart needs an unceasing faith in a Divine power, to enable us by a Divine power to keep it. They cannot understand that it is not to the law, but to a Living Person, that we are now bound, and that our obedience and holiness are only possible by the unceasing faith in His power ever working in us. It is only when this is seen, that we are prepared truly to live in the New Covenant. Its contrast is, the flesh crucified.
Flesh means our sinful human nature.
At his conversion the Christian has generally no conception of the terrible evil of his nature, and the subtlety with which it offers itself to take part in the service of God. The proof that our religion is very much that of the religious flesh, is that the sinful flesh will be found to flourish along with it. It was thus with the Galatians. While they were making a fair show in the flesh, and glorying in it, their daily life was full of bitterness and envy and hatred, and other sins. They were biting and devouring one another.