Rashi on Numbers 16:30/רש"י על במדבר ט״ז:ל׳

1ואם בריאה BUT IF A CREATION — i.e. an entirely new one.

2יברא ה׳ THE LORD WILL CREATE, to slay them by a kind of death by which no man has hitherto died — and what is this new creation?

3ופצתה האדמה את פיה THAT THE EARTH OPEN WIDE HER MOUTH AND SWALLOW THEM, then וידעתם כי נאצו YE SHALL KNOW THAT THEY HAVE PROVOKED the Holy One, blessed be He, and that I have spoken only by authority of the Almighty. Our Rabbis, however, gave the following explanation: ואם בריאה, if there has been a creation, i.e., if there was already a mouth to the earth from the six days of Creation, well and good! but if not, יברא ה׳ the Lord will create one now (Sanhedrin 110a; Nedarim 39b).