As Salamu 'Alaykum
Paul wrote that we reap what we sow:
Gal 6:7 Be not deceived; God is not mocked: for whatsoever a man soweth, that shall he also reap.
In Ezekiel we can read:
"According to their way I will do to them, and according to
their own judgments I will judge them; and they shall know
that I am the LORD." (Ezekiel 7:27b RSV)
Yeshua the son of Mariam is recorded as saying:
Mat 7:12 Therefore all things whatsoever ye would that men should do to you, do ye even so to them: for this is the law and the prophets.
Luk 6:37 Judge not, and ye shall not be judged: condemn not, and ye shall not be condemned: forgive, and ye shall be forgiven:
Luk 6:38 Give, and it shall be given unto you; good measure, pressed down, and shaken together, and running over, shall men give into your bosom. For with the same measure that ye mete withal it shall be measured to you again.
Al Qur'aan says
Ya-Seen
Thou warnest only him who followeth the Reminder and feareth the Beneficent in secret. To him bear tidings of forgiveness and a rich reward. (11) Lo! We it is Who bring the dead to life. We record that which they send before (them), and their footprints. And all things We have kept in a clear Register. (12)
Ya-Seen
This day no soul is wronged in aught; nor are ye requited aught save what ye used to do. (54)
Al-Waqia
Have ye seen that which ye cultivate? (63)
Even the shirk religions have the concept of "Karma" (Reaping what you sow) and "Dharma" (duty) When I was a kid a watched a cartoon called Popeye The Sailor. There was a character in it called Wimpy who was always saying "I will gladly pay you Tuesday for a hamburger today." Well, for Wimpy, Tuesday never came. But in real life "Tuesday" is coming and so is Judgment Day. On that day: Maaliki Yawmid Deen will have the ledger read.
Al-Infitar
Who created thee, then fashioned, then proportioned thee? (7) Into whatsoever form He will, He casteth thee. (8) Nay, but ye deny the Judgment. (9) Lo! there are above you guardians, (10) Generous and recording, (11) Who know (all) that ye do. (12)
Yeshua the son of Mariam said
Joh 13:35 By this shall all men know that ye are my disciples, if ye have love one to another.
If you love someone, you don't want to cause them harm. I firmly believe that the harm we do is not only manifested in our lives (I don't mean reincarnation but lives as in each of us have a life that has a cause and effect) and on Judgement Day, but that it is the result of Ignorance and Ego.
Hopefully, Insha Allah, I have been of some value with the above. There is a word in the Greek called Koiania it is a fascinating study. I once also preached on the words " one another" I was amazed at all the things that Christians are told to do one to another and one another.