to fulfill a promise
私は彼が約束を果たすだろうと確信している。
I’m confident that he will keep his promise.
彼はきっと約束を果たすよ。
He’ll definitely keep his promise.
彼は約束を果たす。
He keeps his promises.
彼はいつも約束を果たす。
He always keeps his promises.
彼は父親との約束を果たすことが出来なかった。
He couldn't keep his promise to his father.