約束を果たすを英語でなんと言うか？

true to word で約束を守る、約束を果たす、約束を実行するの意味になります。0:39 the former Nirvana drummer promised the crowd he would go to hospital and then come back and finish the concert. and an hour later, true to his word, the pro was back on stage with his leg in a cast. フー・ファイターズのデイヴ・グロールは病院で診てもらって、コンサートを最後までやり遂げると約束して（ステージを後にした）、一時間後には約束どおり足にギブスをはめて再びステージに上がった。

ave Grohl breaks his leg at Foo Fighters gig in Sweden but finishes the concert anyway
https://www.youtube.com/watch?v=4xBk26QQ_9Q  1:13 but reports soon surfaced that the biospherians weren't staying true to their word.
Scandal in the Biosphere
https://www.youtube.com/watch?v=MvibriCggOI  8:20 true to his word, local chef Beppe Fontana takes me to Ballaro.
Street food Palermo: A melting pot in the Mediterranean - Street Food

参考リンク
http://bridge-english.blogspot.jp/2015/05/you-have-my-word.html  you have my word
http://bridge-english.blogspot.jp/2011/06/blog-post_07.html  約束を守るを英語でなんと言うか？

練習問題解答
a-7922 true to its name