Musannaf Ibn Abi Shayba 4:207

'Abd al-Samad ibn 'Abd al-Warith narrated to us, from Hawshab ibn 'Aqil, from Ja'far, who said: I asked al-Qasim, "Is it the *sati'* (vertical/spreading) or the *mu'tarid* (horizontal)?" He said, "The *mu'tarid* (horizontal). And the *sati'* (vertical/spreading) is the false dawn."