Charles Ellicott Commentary Mark 10:40

"but to sit on my right hand or on [my] left hand is not mine to give; but [it is for them] for whom it hath been prepared." — Mark 10:40 (ASV)

But it shall be given to them.—Better, omitting the interpolated words, is not mine to give, but to those for whom it has been prepared. Our Lord denies, not the power to give, but that of giving arbitrarily, in a manner other than His Father willed.