Rashi, Ramban #1 and R. Bachye: It refers (not to the command of Hashem, but) to what the Ma'apilim were about to do (to ascending the mountain ? R. Bachye).

Ramban #2 (citing the Ibn Ezra): Contravening the command of Hashem cannot succeed.

Ramban #3 and R. Bachye #1 (both according to Kabalah): The Shechinah ¹ will not allow you to succeed.

R. Bachye #2 (according to Kabalah): It refers to ?Pi Hashem? that precedes it. ²

Targum Yonasan: 'Hashem's word (which generally sides with Yisrael) will not side with you, to enable you to succeed'. ³

Ramban and Seforno: Because Hashem had stated adamantly that they were not to go to Eretz Yisrael. Consequently, if they would go against the word of Hashem, they would be contravening His command. ¹