Musannaf Ibn Abi Shayba 22:249

Waki’ narrated to us, Ubayd Allah ibn Abd al-Rahman ibn Mawhab narrated to us, he said: I heard Muhammad ibn Ka’b al-Qurazi saying: "That I recite 'Idha zulzilat' (Surah az-Zalzalah) and 'al-Qari’ah' (Surah al-Qari’ah), repeating them and reflecting upon them, is more beloved to me than that I recite the Quran rapidly (haddan)."