This applies to all people. Sometimes we demonstrate kindness before any thought of why we are doing it and sometimes we are kind because we feel an obligation to something greater than ourselves.
I’m not well versed in Judiasm, but I don’t believe it holds that we can know the heart of another man. Many kind acts have selfish motivations that we would rather not see or admit exist.
I do know that Judiasm has many rules around behavior, while Christianity simply says, Love thy neighbor. Love is not an act, but inspires and directs one’s behavior.
Regardless of belief structure, I judge my own acts in this way: Am I acting in Love?