וַיֹּ֕אמֶר וּמֶ֖ה לַעֲשׂ֣וֹת לָ֑הּ וַיֹּ֣אמֶר גֵּיחֲזִ֗י אֲבָ֛ל בֵּ֥ן אֵֽין־לָ֖הּ וְאִישָׁ֥הּ זָקֵֽן׃
Metzudat David on II Kings
After she went before him, to Gehzi, and what is this kindness they are doing to her.
Rashi on II Kings
“Then what is there to do for her?” To reciprocate for this favor.