his/her word
J'ai considéré comme acquis qu'il tiendrait sa parole.
I took it for granted that he would keep his word.
He gave me his word.
Mais enfin, tu veux rendre sa parole au prince Andréi ?
But surely you want to give Prince Andrei his word?
— Guerre et Paix (1968)
Je sais qu'il tient sa parole.
I know he keeps his word.