(Rivalry in worldly increase distracteth you until ye come to the graves) [102:1-2].
Muqatil and al-Kalbi said: “This Surah was revealed about two clans of Quraysh: Banu 'Abd Manaf and Banu Sahm. The two clans heaped abuses on each other and this led them to count the respective chiefs and leaders of each clan in order to see which one of them had more. The Banu 'Abd Manaf said: 'We have more leaders, chiefs and members!' The Banu Sahm said the same thing. When it appeared that the Banu 'Abd Manaf had more members, they said: 'Let us also count the dead among us'. They visited the graveyards and counted the dead, and concluded that the Banu Sahm were greater in number, for they were greater in number in the pre-Islamic period”.
And Qatadah said: “This Surah was revealed about the Jews who said: 'We are greater in number than so-and-so, so-and-so and so-and-so', and this claim distracted them until they died misguided”.
Asbab Al-Nuzul by Al-Wahidi , trans. Mokrane Guezzou