Musannaf Ibn Abi Shaybah

Hazrat Abu Saeed Khudri narrates that we used to estimate the duration of the standing (qiyam) of the Prophet (peace be upon him) in the Zuhr and Asr prayers. In the first two rak'ahs of Zuhr, he would recite about thirty verses, and in the last two rak'ahs, he would stand for about half that duration. Similarly, in the first two rak'ahs of Asr, he would stand for the same duration as the last two rak'ahs of Zuhr, and in the last two rak'ahs of Asr, he would stand for about half the duration of the first two rak'ahs.