Abu al-Qasim ibn Bashkuwal: Basri, Trustworthy
Abu Bakr al-Bayhaqi: Trustworthy Imam
Abu Hatim al-Razi: The most reliable of people regarding Thabit and Ali ibn Zayd
Abu Hatim ibn Hibban al-Busti: He memorized all of his hadith, Hammad ibn Zayd was more memorizing, pious, and precise than Hammad ibn Salamah, Hammad ibn Salamah was more religious, virtuous, and God-fearing than Hammad ibn Zayd
Abu Dawud al-Sijistani: I don't think anyone was more knowledgeable in Ayyub than him
Abu Zar'a al-Razi: Hammad ibn Zayd is far more reliable than Hammad ibn Salamah, his hadith is more authentic and precise
Abu 'Abd Allah al-Hakim al-Naysaburi: More reliable than Hammad ibn Salamah
Abu Ya'la al-Khalili: Trustworthy, agreed upon, the Imams were pleased with him
Ahmad ibn Hanbal: Hammad ibn Zayd is one of the Imams of the Muslims, from the people of religion and Islam, and he is more beloved to us than Abd al-Warith
Ahmad ibn Shu'ayb al-Nasai: Trustworthy, Upright
Ahmad ibn Salih al-Jili: Trustworthy, Upright in hadith
Ibn Hajar al-'Asqalani: Trustworthy, Upright, Jurist
Ibn Mandah al-Isbahani: He memorized all of his hadith
Al-Daraqutni: Trustworthy, Upright
Al-Dhahabi: The Imam, one of the flags, he memorized his hadith like water
Abd al-Rahman ibn Mahdi: The Imams of hadith are four: Al-Awza'i, Malik ibn Anas, Sufyan al-Thawri, and Hammad ibn Zayd. And once: I have not seen anyone who has not written more memorizing than him. And once: I have never seen anyone more knowledgeable in the Sunnah nor in hadith than him. And once: I have not seen anyone in Basra more knowledgeable in fiqh than Hammad ibn Zayd
Muhammad ibn Sa'd, the scribe of al-Waqidi: Trustworthy, Upright, Authority, abundant in hadith
Yahya ibn Ma'in: He considered him among the trustworthy Basrans
Yahya ibn Yahya al-Laythi: I have not seen any of the Shaykhs more memorizing than Hammad ibn Zayd
Yazid ibn Zurai' al-'Ayshi: More reliable than Hammad ibn Salamah
Ya'qub ibn Shaybah al-Sadusi: Trustworthy, however, it is known that he is short in chains of narration, and he stops the marfu' (traced back to the Prophet), often doubting its authenticity. He was considered among those who are thorough in Ayyub in particular