Rashi on Numbers 21:35/רש"י על במדבר כ״א:ל״ה

1ויכו אתו AND THEY SMOTE HIM — Moses slew him, as it is related in Treatise Berakhot, in the chapter beginning הרואה‎ (Berakhot 54b): He tore up a rock covering an area of three Parsang and he hurled it at him.