"And all the men that belonged to Korah." Korah was among those who were burned and among those who were swallowed, as it is said, "and the earth swallowed them up together with Korah" (Numbers 26:10). And he was among the burned, among those who offered the incense. And how did this come about? The fire burned him, and he rolled until he came to the place of the swallowing; immediately "and the earth swallowed them up."
How Korah Was Both Burned by Fire and Swallowed by the Earth
Midrash Aggadah, Numbers 16:32
ואת כל האדם. קרח היה מן השרופים ומן הבלועים, שנאמר ותבלע אותם ואת קרח (במדבר כ"ו י'), והיה מן השרופים מן מקריבי הקטרת, וכיצד היה. שרפתו האש ומתגלגל עד שבא במקום הבליעה, מיד ותבלע אותם הארץ: