'Act' in the Bible

He said, "May you be rewarded by the Lord, my dear! This act of devotion is greater than what you did before. For you have not sought to marry one of the young men, whether rich or poor.

(Now this used to be the customary way to finalize a transaction involving redemption in Israel: A man would remove his sandal and give it to the other party. This was a legally binding act in Israel.)