Musnad Ahmad 25:73

Sufyan narrated to us, he said: And Musa ibn Abi Aisha said: I heard Sa'id ibn Jubayr saying: Ibn Abbas said: "When the Quran would descend upon the Prophet, may Allah bless him and grant him peace, he would want to memorize it." Allah, the Almighty and Majestic, said: {Do not move your tongue with it to hasten it. Indeed, upon Us is its collection and its recitation. So when We have recited it, then follow its recitation} [Al-Qiyamah: 16-18].