Book: Siyar A'lam An-Nubala by Ad-Dhahabi - سير أعلام النبلاء ـ الإمام الذهبي

Translation

Ibn Abi Hatim said: My father told us, Harmalah told us: I heard Ibn Wahb say: I vowed that every time I backbit someone, I would fast a day, and it exhausted me. So I would backbite and fast, then I decided that every time I backbit someone, I would give a dirham in charity. Due to my love for dirhams, I refrained from backbiting.

Al-Dhahabi commented: I said: This is indeed how the scholars were, and this is the fruit of beneficial knowledge. Abdullah is a definitive proof, and his hadiths are abundant in the authentic collections and the compendiums of Islam. The recommendation by Al-Nasa’i, known for his strictness in criticism, is enough, where he says: Ibn Wahb is trustworthy; I do not know of him narrating any uncorroborated hadith from reliable narrators.

Then Al-Dhahabi said in "8/15-16":

I said: He included many disconnected and weak narrations in his works, and narrated extensively from Ibn Saman and others like him. Some of the eminent scholars criticized Ibn Wahb for his approach to hadith collection, arguing that he permitted himself flexibility in these matters. Whether he took leniencies he saw permissible or was strict, the fact remains that someone who narrated a hundred thousand hadiths, with few oddities in such extensive work, reached the pinnacle of precision.

He said in "Siyar" "13/365":

The works of Al-Bayhaqi are of tremendous worth and rich in benefits. Rarely has anyone composed a work as perfected as that of Imam Abu Bakr. Scholars should pay attention to his works, especially his "Al-Sunan Al-Kubra." A year or more before his death, he went to Nishapur, attracting a multitude of students who learned his books. They were brought to Iraq and the Levant, and the great scholar Abu al-Qasim al-Dimashqi, along with Abu al-Hasan al-Muradi, took great care in transmitting them and brought them to Damascus.

We were informed that Imam Al-Haramayn Abu al-Ma'ali al-Juwayni said: There is no Shafi'i jurist who does not owe something to Al-Shafi'i, except for Abu Bakr Al-Bayhaqi, for Al-Bayhaqi has bestowed a debt upon Al-Shafi'i through his writings in support of his school.

Al-Dhahabi commented: I said: Abu al-Ma'ali is correct. It is as he said. If Al-Bayhaqi wished, he could have created his own school of thought based on independent reasoning, for he had the capability given his vast knowledge and understanding of differences. Hence, you see him hinting at supporting issues verified by authentic hadiths.