At the battle of Uhud when all the companions deserted the prophet and ran away spreading rumours that the prophet (saas) died, Rasulallah (saas) and Ali ibn abi Talib (as) fought for their lives with 2 other people, 1 was a woman, completely alone against over 50 enemies; Jibrail (as) came down to Muhammad (saas) when Ali’s (as) sword broke and said “What a redeemer you have in the son of Abu Talib (as)” Muhammad (saas) replied with “I am from him and he is from him me” therewhich Jibrail (as) said “I am from the both of you” and thus zhulfiqar was presented to Ali (as), straight from the heavens.

That’s how our story goes, and the sword was passed down and is now with Imam al Mahdi (aj) currently.

EDIT: Oh I forgot to mention, it is interesting to note that even al Tabari narrates this event.