Jamieson, Fausset and Brown on Numbers 14:21

21. all the earth shall be filled with the glory of the Lord--This promise, in its full acceptation, remains to be verified by the eventual and universal prevalence of Christianity in the world. But the terms were used restrictively in respect to the occasion, to the report which would spread over all the land of the "terrible things in righteousness" [Psa 65:5] which God would do in the infliction of the doom described, to which that rebellious race was now consigned.