Tirmidhi

English Commentary:
1:
Regarding which prayer is meant by "the middle prayer" (salat al-wusta), various hadiths have been narrated. The correct opinion is that what is meant is the ‘Asr prayer (salat al-‘asr). This is also the view of the majority of the Companions and the Followers (Tabi‘in).
Imam Abu Hanifah and
Imam Ahmad have also adopted this position.

2:
The well-known position of Imam Malik and Imam Shafi‘i is also this.

Note:
(Supported by the previous hadith, this is sahih li-ghayrihi (authentic due to corroborating evidence).
There is a difference of opinion regarding Hasan al-Basri’s hearing from Samurah radi Allahu anhu.
Also, Qatadah and Hasan al-Basri are mudallis (those who sometimes conceal their sources), and this narration is by way of ‘an‘anah (ambiguous transmission)).