Verse 31
For their rock - The gods and pretended protectors of the Romans.
Is not as our Rock - Have neither power nor influence like our God.
Our enemies themselves being judges - For they often acknowledged the irresistible power of that God who fought for Israel. See Exo 14:25; Num 23:8-12, Num 23:19-21; 1Sam 4:8.
There is a passage in Virgil, Eclog. iv., ver. 58, very similar to this saying of Moses: -
Pan Deus Arcadia mecum si judice certet,
Pan etiam Arcadia dicat se judice victum. "Should the god Pan contend with me," (in singing the praises of the future hero, the deliverer, prophesied of in the Sibylline books), "were even
Arcadia judge, Pan would acknowledge himself to be vanquished, Arcadia herself being judge."