The Imam has narrated the chain of transmission of Hajjaj al-Sawwaf. The Imam says that I heard Muhammad bin Yahya saying that Hajjaj al-Sawwaf is trustworthy and a hafiz (memorizer of hadith).
Hadith Referenceصحيح ابن خزيمه / جماع أبواب صلاة الكسوف / 1376