Albert Barnes Commentary Judges 5:15

"And the princes of Issachar were with Deborah; As was Issachar, so was Barak; Into the valley they rushed forth at his feet. By the watercourses of Reuben There were great resolves of heart." — Judges 5:15 (ASV)

Even Issachar ... - that is, “and, as well as Issachar, Barak also with the tribes of Zebulun and Naphtali, rushed down on foot from Mount Tabor into the valley to attack the iron chariots of Sisera.”

For the divisions - Better: “among the brooks.” Reuben ought to have followed in this catalogue of patriots, but with that abruptness for which this poem is so conspicuous, Deborah refers to his absence instead.