Or HaChaim on Numbers 14:44/אור החיים על במדבר י״ד:מ״ד

1 ויעפילו לעלות אל ראש ההר, But they presumed to go up to the top of the mountain, etc. They erred in thinking that by ascending the mountain they could demonstrate their faith in G'd and that as a result G'd would save them. G'd was not impressed, 1) for their punishment was still too recent to have run its course, and 2) the decree had been made absolute so that G'd could not reverse it. Please compare what I have written on this subject in Deut. 1,43.