A short proof of a theorem due to O. Gabber

A very short proof of an unpublished result due to O. Gabber is given. More presicely, let $R$ be a regular local ring, containing a finite field $k$. Let $\mathbf{G}$ be a simply-connected reductive group scheme over $k$. We prove that a principal $\mathbf{G}$-bundle over $R$ is trivial, if it is trivial over the fraction field of $R$. This is the mentioned unpublished result due to O. Gabber. We derive this result from a purely geometric one proven in another paper of the author and stated in the Introduction.