Jamieson, Fausset and Brown on Judges 4:8

8. Barak said unto her, If thou wilt go with me, then I will go--His somewhat singular request to be accompanied by Deborah was not altogether the result of weakness. The Orientals always take what is dearest to the battlefield along with them; they think it makes them fight better. The policy of Barak, then, to have the presence of the prophetess is perfectly intelligible as it would no less stimulate the valor of the troops, than sanction, in the eyes of Israel, the uprising against an oppressor so powerful as Jabin.