What is Fide-Jubere?

Legal Definition
In the civil law. To order a thing upon one's faith; to pledge one's self; to become surety for another. Fide-jubes t Fide-jubeo: Do you pledge yourself? I do pledge myself. Inst 3, 16, L One of the forms of stipulation.
-- Black's Law Dictionary
Legal Definition
To become surety.
-- Ballentine's Law Dictionary