Abu Ja'far Al-'Uqayli: He is not followed, nor is anything from his hadith
Abu Hatim Al-Razi: His hadith is written, but not used as evidence
Abu Hatim Ibn Hibban Al-Busti: He was a rejecter, calling for rejection, and he was among those who narrated problematic narrations from the trustworthy narrators, and he contradicted the established narrations in what he narrated from the trustworthy narrators. So, he is unworthy of being used as evidence. And upon consideration, if someone considers him as evidence, I hope that he will not be criticized for that.
Abu Dawud Al-Sijistani: He was from Herat, they abandoned his hadith, he is nothing
Abu 'Abd Allah Al-Hakim Al-Naysaburi: His strange and objectionable hadiths are the fault of his son Khalid, and the blame falls on him
Abu Nu'aym Al-Asbahani: Those strange and objectionable narrations that Salih Ibn Muhammad saw in Herat from the hadith of Hayaj, the blame for them is not on Hayaj, but the blame is on his son Khalid, and the burden is on him
Ahmad Ibn Hanbal: Abandoned in hadith
Ahmad Ibn Shu'ayb Al-Nasai: He was from Herat, weak
Ibn Hajar Al-'Asqalani: Weak, his son Khalid narrated very strange and objectionable narrations from him
Al-Daraqutni: Very weak
Al-Dhahabi: Weak
Salih Ibn Muhammad Juzra: They abandoned his hadith, and once: A sheikh from Herat, his hadith is rejected, there is no meaning in it, nothing is written from his hadith except for three hadiths for consideration. And I did not know that he was so rejected in hadith until I went to Herat and saw many strange and objectionable hadiths among the people of Herat
Muhammad Ibn Yahya Al-Dhuhali: He is trustworthy in our view
Makki Ibn Ibrahim Al-Tamimi: We do not know Hayaj except as trustworthy, truthful, and knowledgeable
Yahya Ibn Ahmad Al-Harawi: Everything that is rejected from Hayaj is from the side of his son Khalid, for Hayaj himself is trustworthy
Yahya Ibn Ma'in: He is nothing, and once: He is not trustworthy, and once: He was from Herat, weak in hadith, and once: His hadith is nothing
Ya'qub Ibn Sufyan Al-Faswi: I used to hear our companions weakening them