Presidents, all over the world, have immunity from prosecution. In many countries, this immunity extends beyond their term of office. It doesn't have to be a written rule, it's just a good practice to leave former Presidents enjoy their retirement. 

Persecuting & prosecuting a former President creates a bad precedent & leads some Presidents to cling to power.

President Jacob Zuma should be left to enjoy his retirement in peace, it's the right thing to do. Jailing him won't add any value to anyone's life and it leads to deeper divisions in an already divided society.

President Ramaphosa should do the noble thing: Pardon President Jacob Zuma & allow him to enjoy his retirement in peace.