Why not begin your speech by giving an example of how you helped someone, and then someone helped you. The idea is that if you are a good person and treat people well, then others will treat you well. It's also known as karma, or good will.
Or the idea of karma in Indian philosophy. Both Buddhism and Hinduism have the idea that whatever deeds you do in life will lead to consequences, particularly moral consequences. If you give money away in this life, then in the future you may be wealthier and in a positon to help others more. If you are miserly or steal from others, then in the future you will have even less.
Of course, this won't convince anyone who doesn't already believe in karma, but it may be useful to remember that ideas of justice - whether cosmic or man-made - often come down to giving people what they deserve.
I think that you should either A) focus on personal life or B) look at history or current events. Both of these could give you ideas for examples of people (or countries) getting what they deserve.
You might also start with some sort of fable. Aesop's fable about the mouse and the lion can be seen as an example of this idea. After telling that, you could move into examples from real life.
Thanx teachers but i'm in primary and i don't know hoe to present the speech which is due next Thursday