Promissory

[Sarah]

Containing a promise or binding declaration of something to bedone or forborne. Promissory note (Law), a written promise to pay tosome person named, and at a time specified therein, or on demand, orat sight, a certain sum of money, absolutely and at all events; --frequently called a note of hand. Kent. Byles. Story.

[Britney]

Conveying or implying a promise.