It is the flesh of the lizard. Thereupon Allah's Messenger (way peace be upon him) said: Eat, for it is lawful, but it is not my diet.
Sahih Muslim Book 34, Hadith 61
← Previous Hadith " A lizard was brought to Allah's Messenger (ﷺ) but he neither ate that nor declared it unlawful." And in the hadith transmitted through Usama (the words are):" The man (inquirer) was standing in the mosque and Allah's Messenger (ﷺ) was sitting on the pulpit."

Sahih Muslim Book 34, Hadith 60 Next Hadith → Al-Sha'bi (one of the narrators) asked me if I had heard the hadith transmitted on the authority of Hasan from the Prophet (ﷺ). He said: I sat in the company if Ibn 'Umar for two years or a year and a half but I did not hear narrated from Allah's Apostle (ﷺ) but this one (pertaining to the flesh of the lizard) as narrated by Mu'adh.

Sahih Muslim Book 34, Hadith 62