The story is mentioned in Surat Al-Fil, verses 1-5.

Allah says :

((Have you not seen how your Lord dealt with the companions of the elephant? (1) Did He not cause their scheming to go astray? (2) And sent upon them flocks of birds (3) pelting them with stones made of obsidian). (4) Then He made them like edible chaff (5)))

the story:

Yemen belonged to Al-Najashi, King of Abyssinia. The governor of Yemen (Abraha) built a great church, and wanted to change the direction of the Arab pilgrimage. He makes them make pilgrimage to this church instead of the Sacred House of God. So he wrote to the Negus: I have built for you, O king, a church the likes of which was not built for a king who was before you, and I am not ready to direct the Arab pilgrimage to it. But Arabs refused that, and they had pride in their beliefs and their ancestors. They are the children of Abraham and Ishmael, so how could they leave the house that their fathers built and go on pilgrimage to a church built by a Christian! It was said that an Arab man went and insulted the church. And the Banu Kenanah killed the messenger of Abraha who came asking them to perform Hajj to the church.

So Abraha dicided to demolish Kaaba. He prepared a large army, and placed at its forefront an elephant famous among them, whose name is said to be Mahmoud. Arabs Vazmt to be said Abraha. The first person to go out to meet him was a noble man from Yemen called Dhu Nafar. He called his people and they answered him and joined forces with Abraha’s army. But he was defeated and taken prisoner to Abraha.