Christians don’t believe in Karma but they do know that the thinking behind Karma does work. For Christians and get the “whats goes around comes around” or the “do it and it will come back to you or them” is answered in a single and very well-known piece of Scripture.
Matthew 7:12 is one of the most well-known verses of the bible that has made its way into the lives of those who wouldn’t know a bible from a baseball bat. The powerful and very true verse reads “So in everything, do to others what you would have them do to you, for this sums up the Law and the Prophets.” (NIV) and reads even better in The Message Bible “Here is a simple, rule-of-thumb guide for behavior: Ask yourself what you want people to do for you, then grab the initiative and do it for them. Add up God’s Law and Prophets and this is what you get.”
Basically it is the fact that what you do for or to others should be as you would want any other to do for you if you were in their shoes. It says little about the karma part about things coming back to you to haunt you or bless you but further study will show that Matthew 7:12 has to be part of a way of life. The Message translation says “grab the initiative” and this means being proactive and being kind, generous or helpful can easily be done for anyone whether they deserve it or not.
God does not set out to send bad things our way nor does He punish us, the law and courts of the land will surely punish us for wrongdoing and others in the world will punish us for harm done and it has nothing to do with God who merely allowed the mechanisms for justice to be established.
On the other had God does bless us for good deeds, but it doesn’t mean unlike those who believe in Karma that whatever good you do will be equally rewarded. For a Christian the absolute reward lies in Heaven and is an eternal life at the right hand side of God but blessings in life do tend to follow. Making the effort to do what you would expect or at least hope someone to do for you does get you seen and noticed and that can lead to steps in the right direction.
Karma for a Christian may not exist but God does bless those who follow is commands and do as he asks. Often the reward is not as one expects, unlike Karma where a like for like is expected.
Trust is God in your life, do unto others as you would expect them to do for you, be proactive but do not seek or expect a return or reward and see your life around as God’s word in its fullness promises.