A man of his word or a woman of her word.

言出必行的男人，言出必行的女人。

He was a man of his word.

他是守信的人。

Federer promised to read Twitters'favorite and he is a man of his word.

费德勒承诺会去看大家推特上推荐的名胜，他没有食言。

You might not want to believe this, but Elijah is a man of his word.

你可能不相信，但以利亚是个守信用的人。