Harb al-Karmānī said: “Aḥmad ibn Ḥanbal was asked about Ṣāliḥ ibn Kaysān and exclaimed, ‘Bakh, bakh!’—an expression of the highest praise.
ʿAbd Allāh ibn Aḥmad reported that, in relation to Ṣāliḥ, his father said: “He was older than al-Zuhrī, and he had met Ṣāliḥ ibn ʿUmar.”
Isḥāq al-Kawsaj transmitted from Yaḥyā ibn Maʿīn that he declared Ṣāliḥ “trustworthy.”
ʿAbbās likewise reported from Yaḥyā that he said: “There is no fault in him with respect to his narrations from al-Zuhrī.”
Yaḥyā also affirmed that Ṣāliḥ had indeed heard from Ibn ʿUmar, though he added: “In narrations from al-Zuhrī, I prefer Maʿmar.”
Yaʿqūb ibn Shaybah related—through Aḥmad ibn al-ʿAbbās—that Yaḥyā ibn Maʿīn said: “Among al-Zuhrī’s disciples none is more firmly grounded than Mālik; after him comes Ṣāliḥ ibn Kaysān, then Maʿmar, then Yūnus.”
Yaʿqūb further remarked: “Ṣāliḥ is trustworthy, solid.”
ʿAlī ibn al-Madīnī said: “He was older than al-Zuhrī and had seen Ibn ʿUmar.”
Ibn Abī Ḥātim quoted his father as saying: “I prefer Ṣāliḥ to ʿUqayl because he was a Ḥijāzī and the elder of the two. He saw Ibn ʿUmar, he is reliable, and he is counted among the Successors.”
Al-Nasāʾī, Ibn Khirāsh, and others likewise deemed him “trustworthy.”
Maʿmar narrated from Ṣāliḥ: “I and Ibn Shihāb once met while seeking knowledge and agreed that we should write down the Sunnah. So we committed to writing everything we heard from the Prophet—peace and blessings be upon him.
Then Ibn Shihāb said, ‘Let us also record what has reached us from his Companions.’
I replied, ‘That is not Sunnah.’
He said, ‘Indeed, it is Sunnah.’
So he wrote, whereas I did not; in the end he succeeded and I lost out.”
Al-Humaydī, transmitting from Sufyān, said: “ʿAmr used to report the ḥadith of Ṣāliḥ ibn Kaysān concerning the Prophet—peace and blessings be upon him—alighting at al-Abṭaḥ. The chain was: from Nāfiʿ, the client of Abū Qatādah, on the authority of Abū Qatādah.
Later Ṣāliḥ himself arrived, whereupon ʿAmr told us: ‘Go and ask him about this ḥadith.’
So we went to him and inquired.”
Yaʿqūb ibn Ibrāhīm ibn Saʿd related from his father: “Ṣāliḥ ibn Kaysān…”