Behest

n. [be and hest; A-S. behæs.] 1. That which is willed or ordered; command; mandate; injunction. To do his master's high behest. W. Scott. 2. A vow; a promise. [Obs.] The time is come that I should send it her, if I keep the behest that I have made. Paston.

To vow. [Obs.] Paston.