Ibn 'Abbas has reported this hadith on the authority of Ubayy b. ka'b that Allah's Apostle (ﷺ) used to recite this.
The Book of Virtues - Sahih Muslim 2380 e
In the name of Allah, the Most Gracious, the Most Merciful. This narration transmitted through the esteemed chain of Ibn 'Abbās from Ubayy ibn Ka'b (may Allah be pleased with them both) informs us of the recitation practice of the Prophet Muhammad (peace be upon him).
The scholars of hadith have established that this tradition demonstrates the importance of following the Prophet's example in Qur'anic recitation. Ubayy ibn Ka'b was among the foremost reciters of the Qur'an, and his transmission carries particular weight in matters of recitation.
Imam al-Nawawi, in his commentary on Sahih Muslim, explains that such narrations guide us to emulate the Messenger of Allah in both the manner and content of his recitation. The unspecified nature of what was recited indicates the comprehensive nature of following his example in all recitations.
This hadith falls under the broader chapter of virtues, teaching us that the Prophet's practices themselves constitute virtues to be followed. The chain of transmission through Ibn 'Abbās and Ubayy ibn Ka'b represents two of the most knowledgeable companions regarding Qur'anic matters.