The english translation of Tafsir Ibn Kathir is abridged and omits some of the hadith cited after this sentence: 

> There are Hadiths that mention that Allah took Adam's offspring from his loins and divided them into those on the right and those on the left.

As for this sentence:

> At-Tirmidhi said, "This Hadith is Hasan Sahih, and it was reported from various chains of narration through Abu Hurayrah from the Prophet ''. Al-Hakim also recorded it in his Mustadrak, and said; "Sahih according to the criteria of Muslim, and they did not record it.'' 

It is regarding the hadith that has been quoted just before it:

>  At-Tirmidhi recorded that Abu Hurayrah said that the Messenger of Allah said,
>
> [ arabic text ]
>
> **(When Allah created Adam ...**
>
>  **... his offspring made mistakes.)** 

This is from [Jami at-Tirmidhi, Kitab al-Tafsir, 3076](https://sunnah.com/urn/740820) and has also been collected by al-Hakim Nishapuri  in his [Mustadrak ala al-Sahihain, Kitab al-Tafsir, Surah Al-A'raf, 3257](https://al-maktaba.org/book/2266/3377#p1). Mustadrak is a collection of hadith that the author claims to be Saheeh on the conditions of Bukhari and Muslim.