Abu Bakr al-Bayhaqi: He only narrates from trustworthy narrators.
Abu Hatim al-Razi: Trustworthy, حافظ (Preserver of Hadith).
Abu Hatim ibn Habban al-Busti: One of the leaders of his time, known for his preservation, piety, understanding, and virtue.
Abu Zar'a al-Razi: One of the trustworthy and preserving narrators.
Abu Ya'la al-Khalili: He is an Imam without any doubt. Al-Thawri used to be amazed by his memorization. All the Imams considered him a reliable source and said: 'Whoever abandons Yahya, we abandon him'.
Ahmad ibn Hanbal: My eyes have not seen anyone like him. Once he said: 'He is the ultimate authority in Basra in terms of verification.' Another time: 'I have not seen anyone like him in this matter.' And another time: 'How precise and careful he was! He was a Hadith scholar.' And he praised him with the best praise. Once he said: 'I have not seen anyone who makes fewer mistakes than him.' And he mentioned him in his Musnad and said: 'Trustworthy.'
Ahmad ibn Shu'ayb al-Nasai: Trustworthy, reliable, and pleasing.
Ahmad ibn Salih al-Jili: Trustworthy, pure in Hadith, he would only narrate from trustworthy narrators.
Ibrahim ibn Muhammad ibn Ya'qub al-Taymi: I have not seen anyone more knowledgeable about narrators than him.
Ibn Hajar al-'Asqalani: Trustworthy, meticulous, حافظ (Preserver of Hadith), Imam, Exemplary.
Ibn Manjawaih al-Isbahani: One of the leaders of his time, known for his preservation, piety, understanding, and virtue. He paved the way for the people of Iraq in the field of Hadith, delved deep into researching trustworthy narrators, and abandoned the weak ones.
Al-Daraqutni: He is preferred over 'Abd al-Rahman ibn Mahdi because he was the most generous of people; if he had any doubt about a Hadith, he would abandon it.
Al-Dhahabi: The great حافظ (Preserver of Hadith), he was a leader in knowledge and deeds. And once he said: 'The great Imam, the leader of the believers in Hadith.'
Abd al-Rahman ibn Mahdi: You will not see his like. I have not seen anyone better at understanding and seeking Hadith than him. Ibn Ma'in narrated from him: 'I have not seen anyone who rejects bad narrations better than Yahya ibn Sa'id.' Ibn al-Mubarak narrated that he said: 'There is no one among our companions who wrote Hadith from me, memorized it, and narrated it like Yahya ibn Sa'id, Sufyan ibn 'Uyainah, and Yazid ibn Zurai'.
Ali ibn al-Madini: I have not seen anyone more reliable than him. And once he said: 'I have not seen anyone more knowledgeable about narrators than him.'
Muhammad ibn Bashar al-'Abdi: Imam of his time.
Muhammad ibn Sa'd, the scribe of al-Waqidi: Trustworthy, reliable, highly regarded, and an authority.
Muhammad ibn 'Amr al-Mawsili: Hadith scholar.
Yahya ibn Ma'in: He is above 'Abd al-Rahman ibn Mahdi. In a narration by Ibn Mahriz from him, he said: 'By Allah, he is trustworthy.'