Al-Ajlaḥ corroborated the report, transmitting it from ʿAbd Allah on the authority of his father.

Muḥammad ibn ʿĪsā ibn al-Ṭabbāʿ said: Muʿādh ibn Muḥammad ibn Muḥammad ibn Ubayy ibn Kaʿb narrated to us, from his father, from his grandfather, from Ubayy:
The Messenger of Allah ﷺ said, “O Abū al-Mundhir! I have been commanded to present the Quran to you.”
I replied, “I believe in Allah, I embraced Islam at your hand, and it was from you that I learned.”
He repeated the statement, so I asked, “O Messenger of Allah, was I mentioned there?”
He said, “Yes—your very name and lineage—in the Highest Assembly.”
I said, “Then recite, O Messenger of Allah.” (1)

Abū Ḥātim al-Rāzī also transmitted it from Ibn al-Ṭabbāʿ, who said: “Muʿādh ibn Muḥammad ibn Muʿādh ibn Ubayy narrated to us….”

Sufyān reported—through al-Aʿmash, from Abū Wāʾil, from Masrūq—on the authority of ʿAbd Allah ibn ʿAmr, as a marfūʿ hadith:
“Learn the Quran from four: Ibn Masʿūd, Ubayy, Muʿādh, and Sālim, the freedman of Abū Ḥudhayfa.” (2)

Abū Dāwūd recorded—through the tradition of Ibn ʿUmar—that the Prophet ﷺ once led a prayer and became unsure of the recitation. When he finished he said to Ubayy, “Did you pray with us?”
He answered, “Yes.”
He said, “Then what kept you from correcting me?” (3)