8. Muhammad ibn al-Hassan has narrated from Sahl from Ahmad ibn Muhammad from ibn abu Nasr who has said the following:

“I once said to abu al-Hassan , that our people have differences about optional Salah (prayer). Certain ones among them say it is forty-four and others perform fifty. Please tell me about what you perform and how is it, so I can do similarly. He (the Imam) said, ‘I perform fifty-one Rak‘at.’ He (the Imam) then said, ‘Hold on to it.’ He (the Imam) counted with his hand saying, ‘Zawal (declining of the sun toward the west at noontime) is eight. There are four after al-Dhuhr, four before al-‘Asr, two after al-Maghrib, two before al-‘Isha’, two after al-‘Isha’ in a sitting position which are counted as one Rak‘at in a standing position. There are eight Rak‘at of nightly Salah (prayer), three of al-witr and two at dawn. Obligatory Salah (prayer) is seventeen Rak‘at and this becomes fifty-one Rak‘at.’”