"A kind man benefits himself, but a cruel man brings trouble on himself." Proverbs 11:17
Kindness builds up those who are most interested in building up others. Cruel people try to give themselves a boost by harming others but that doesn't work out as harming others will eventually cause trouble for the cruel person. Have people been unkind to you? Maybe it's because you haven't made an effort to be kind to others? God does not take your kindness for granted. Biblical truth says that God helps those who help others. Do you qualify? Then they and you will benefit