The Tābiʿū al-Tābʿīn (Arabic: تَابِعُو ٱلتَّابِعِينَ, singular تَابِعُ ٱلتَّابِعِينَ) is the generation after the Tābi‘ūn in Islam.
The first generation of Muslims are called the companions of Muhammad. The second generation of Muslims are called tābi‘ūn "Successors". The third generation are called tabi‘ū al-tabi‘īn "successors of the Successors".[1] The three generations make up the Salaf, the "Ancestors", of Islam.
Definition according to the Sunnis
The Sunnis define a successor of the Successors as a Muslim who:
Saw at least one of the tābiʿ.
Was rightly guided (is a Sunni)
Died in the state of Sunnihood
In a Hadith, The Nabi Muhammad said, "The best people are those living in my generation, then those coming after them, and then those coming after." Sahih Bukhari[2]