Assalaamu alaykum. I heard that Ath-Thahabi criticized Ibn Taymiyyah after having praised him. Why?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.

Imaam Ath-Thahabi praised Shaykh Ibn Taymiyyah,   excessively, and he wrote a wonderful biography of him in Taareekh Al-Islam, and he said in his glossary of scholars (Mu'jam ash-Shuyookh), “He is greater than being referenced with a biography by someone like me; if I were to swear between Ar-Rukn (i.e. the corner where the Black Stone is in the wall of the Ka'bah) and the Maqaam (i.e. the Maqaam of Ibraaheem close to the Ka'bah), then I would swear that I have never seen the like of him and that He had never seen someone like himself.” He also said, “Any hadeeth which Ibn Taymiyyah does not know of is not a hadeeth.”

As regards the criticism which you referred to in the question, it was mentioned in a paper (dissertation) that is attributed to Imaam Ath-Thahabi and which is called 'Bayaan Zaghal Al-Ilm wat-Talab' or 'An-Naseehah Ath-Thahabiyyah'. However, it is falsely attributed to him. Shaykh Muhammad ibn Ibraaheem Ash-Shaybaani wrote a paper refuting the attribution of this paper to Imaam Ath-Thahabi which he named 'At-Tawdheeh Al-Jaliyy fee Ar-Radd ‘Ala An-Naseehah Ath-Thahabiyyah Al-Manhoolah ‘Ala Al-Imaam Ath-Thahabi'.

Allaah knows best.