John Gill Commentary Deuteronomy 1:28

"Whither are we going up? our brethren have made our heart to melt, saying, The people are greater and taller than we; the cities are great and fortified up to heaven; and moreover we have seen the sons of the Anakim there." — Deuteronomy 1:28 (ASV)

Where shall we go up ?
&c.] What way can we go up into the land? where is there any access for us? the mountain we are come to, and directed to go up, is possessed by the Amorites, a strong and mighty people, who keep and guard the passes, that there is no entrance:

our brethren have discouraged our hearts ;
ten of the spies; for Joshua and Caleb encouraged them with very powerful arguments, which had they listened to, it would have been well for them:

saying, the people is greater and taller than we ;
more in number, larger in bulk of body, and higher in stature:

the cities are great, and walled up to heaven ;
an hyperbolical expression; their fears exaggerated the account of the spies; they told them they were great, large, and populous, walled, and strongly fortified; which appeared in their frightened imaginations as if their walls were so high as to reach up to heaven, so that it was impossible to scale them, or get possession of them:

and, moreover, we have seen the sons of the Anakims there ;
the giants so called from Anak, the son of Arba, the father of them; their names are given, (Numbers 13:22Numbers 13:23) (Joshua 14:15) (Joshua 15:13Joshua 15:14) .