His offer to go with her shows the truth of his faith, for which he is praised, Hebrews 11:32; but his refusal to go without her shows the weakness of his faith, that he could not trust God's bare word, as he ought to have done, without the pledge of the presence of his prophetess, whom he thought God would preserve and deliver, and himself for her sake.
Related Commentaries of Judges 4:8
Judges 4:8
8 And Barak said unto her, If thou wilt go with me, then I will go: but if thou wilt not go with me, then I will not go.