Oneness of humanity

Sikhs believe in the oneness of humanity. This is the belief that all humans are equal because they were created by Waheguru, which means ‘Wonderful God’ or ‘Wonderful Lord’. Sikhs also believe that Waheguru is present in every individual as the divine spark. The words ‘atma’, ‘soul’ and ‘light’ are sometimes used for this divine spark. Because Sikhs believe that every living thing has a part of God within them, they believe that all humans should be treated equally and with respect.

quote
If a beggar cries out at the door, the Master hears it in his mansion. Whether He receives him or pushes him away, it is the Gift of the Lord’s Greatness. Recognise the Lord’s Light within all, and do not consider social class or status; there are no classes or castes in the world hereafterGuru Granth Sahib 349

The belief that all humans are equal affects how Sikhs treat people. Everybody is treated the same, whatever their gender, age, status or faith.

Question

Why do Sikhs believe in the oneness of humanity?

Sikhs believe that everyone was created by God (Waheguru), and also that all humans have the divine spark of God within them.