Sforno on Numbers 14:41/ספורנו על במדבר י״ד:מ״א

1?למה זה עוברים את פי ה' והיא לא תצלח; by defying G’d in this manner you will not merely be guilty of a sin due to your trying to indulge your whims, but to the sin of deliberately trying to cause G’d to become angry. (the worst category of sin)