Qurban first started with Prophet Ibrahim and his son Prophet Ismail. Prophet Ibrahim had a dream that he was sacrificing his son Ismail. When he woke up he knew that it was an order from Allah ﷻ . He told his son about this order and Ismail replied: “dear father, if Allah ﷻ has ordered it, then you must obey, so sacrifice me. Do not fear, with the help of Allah ﷻ , I shall be brave.”
Ibrahim prepared to slaughter his son. Just as Ibrahim was about to do so, he heard a voice say: “you have shown your good intentions and you have already fulfilled Allah’s ﷻ command.” An animal was then sent down for Ibrahim to sacrifice instead. Ismail was saved and Ibrahim understood that he was being tested.
To remember this event, Muslims celebrate Eid al-Adha every year and like Prophet Ibrahim and his son and Prophet Muhammed ﷺ after them, we sacrifice an animal.