Al-Fil 105:2

Abraha was a Christian ruler of Yemen in southern Arabia in the sixth century A.D. Out of religious fanaticism, he attacked Makkah in the year 570 A.D. (the year of the Prophet’s birth) with a view to destroying the Kabah by demolishing it. He had with him an army of sixty thousand soldiers and about a dozen elephants. That is why they were called ‘the People of the elephant’. As these people approached Makkah, the elephants refused to move ahead. Besides that, flocks of birds flew over them carrying pebbles in their beaks and claws. They showered these pebbles on Abraha’s army and the whole army was afflicted by a strange disease. The army was terrified and took flight. But many of its soldiers, including Abraha died on the way. This was a sign that whoever set himself against the Prophet or his mission would be defeated like the army of the elephants. This was Almighty God’s way of showing that the Prophet was associated with domination. The divine book revealed to him would be preserved by God for all time to come for the guidance of all mankind.

Tafsir Ibn Kathir (abridged, English).