Grace according to law

In lesson Hassan and Din 1, you explain that Din is an action according to rules and Chesed is an action that does not follow the rules.
According to the law, I am not obligated to give charity, and therefore if I give, I am performing an act of kindness (if the commandments of charity are ignored).
 
My question is, is it true that kindness is an action that is not according to political law, but it is an action that is according to moral law. In other words, I am morally obligated to act according to kindness. And according to this, again kindness is not a voluntary action, but I am obligated to act according to kindness.
So how does it work out that on the one hand the connotation of kindness is an act of voluntary benefit, etc., and on the other hand it is not voluntary but rather a moral obligation?