Musannaf Ibn Abi Shaybah

Ibrahim says that the predecessors used to count these rak‘ahs among the Sunnah: four before Zuhr, two after Zuhr, two after Maghrib, two after ‘Isha, and two before Fajr. Ibrahim says that they considered the two rak‘ahs before ‘Asr as recommended, but did not regard them as Sunnah.