Fiqh-us-Sunnah Volume 2, Supererogatory Prayer, Fiqh 2.078.
Section : Proximity of the sutrah.
Al-Baghawi says: “The people of knowledge prefer that the sutrah be so close that there is only enough space to make the sajdah, and the same applies to the distance between the rows in the prayer. “
In the hadith mentioned in the beginning of this section it is stated: “And he should be close to it.”
Bilal reports that between the Prophet and the wall in front of him there was a distance of three arm spans. This is related by Ahmad and anNasa’i, and al-Bukhari has recorded something similar.
Sahl ibn Sa’d says: “Between the Messenger of Allah [and his sutrah] was enough space for a sheep to pass.” This is related by al-Bukhari and Muslim.