Grading: This report is "sahih"; however, this chain is "hasan" because of Ahmad bin 'Abd al-Jabbar.
Technical note / Defect ('illah): In the chain, "Abu Mu'awiyah" refers to Muhammad bin Khazim al-Darir, and "'Abd Allah" refers to the Companion of the Messenger, 'Abd Allah bin Mas'ud (may Allah be pleased with him).

Reference / Source: al-Bayhaqi narrated it in "al-Madkhal ila al-Sunan al-Kubra" (125) via Abu Sa'id bin Abi 'Amr and Abu 'Abd Allah al-Hakim, with this same chain.

Reference / Source: Ibn Sa'd transmitted it in his book "al-Tabaqat" (2/ 315) through Abu Mu'awiyah, with this same chain.

Reference / Source: Imam al-Tabari narrated it, in the Musnad of Ibn 'Abbas section of "Tahdhib al-Athar" (1/ 173), through Abu al-Sa'ib Salm bin Junadah, from Abu Mu'awiyah (Muhammad bin Khazim al-Darir), with this same chain.

Reference / Source: Ibn Sa'd (2/ 315), Abu Khaythamah in "al-'Ilm" (48), Ibn Abi Shaybah (12/ 110), Ahmad in "Fada'il al-Sahabah" (1559, 1562, 1861, 1863), Ya'qub bin Sufyan in "al-Ma'rifah wa-l-Tarikh" (1/ 495, 496), Ibrahim al-Harbi in "Gharib al-Hadith" (1/ 152), al-Tabari (1/ 172, 173), al-Bayhaqi in "al-Madkhal" (126) and "Dala'il al-Nubuwwah" (6/ 193), and al-Khatib in "Tarikh Baghdad" (1/ 524-525) narrated it through various routes from Sulayman bin Mihran al-A'mash.
Details of the narration: Some narrators added in it that (Ibn Mas'ud) used to say: "What an excellent interpreter of the Qur'an Ibn 'Abbas is." This addition will come on its own later with the author (al-Hakim) at number (6424).

Note / Clarification: In the text the word "ma 'asharahu" occurs, while in some sources it is "ma 'aasharahu"; both have the same meaning, namely: "If Ibn 'Abbas had been equal to us in age, none of us would have reached even a tenth of his knowledge." This explanation was given by Ibrahim al-Harbi.