Imaam Muslim (rahimahullah) mentioned, “I presented this kitaab of mine (Saheeh Muslim) to Imaam Abu Zur’ah (rahimahullah). Every Hadith in this kitaab, in which he found some weakness and showed me some problem – I left it out and did not include it in the kitaab, and every Hadith regarding which he said, ‘It is saheeh (authentic), and there is no weakness in it,’ – then these are the Ahaadith which I kept in my kitaab.” (Siyar A’laamin Nubalaa 12/568)