Eminent Ustaads:

Allah Ta‘ala had blessed Imaam Abu Dawood (rahimahullah) to acquire the blessed hadith of Rasulullah (sallallahu ‘alaihi wasallam) from many eminent Ustaads. Haafiz Ibnul Hajar Asqalaani (rahimahullah) has mentioned that the Ustaads from which Imaam Abu Dawood (rahimahullah) as reported Ahaadith, in his Sunan and in other kitaabs as well, are approximately three hundred in number. (Tahzeeb-ut-Tahzeeb 4/172)

Among the well-known Ustaads of Imaam Abu Dawood (rahimahullah) were the likes of Imaam Ahmed bin Hambal, Imaam Qutaibah bin Sa’eed, Imaam Ali bin Madeeni, Imaam Yahya bin Ma’een, Imaam Ishaaq bin Raahwayh and Imaam Abdullah bin Maslamah Qa’nabi (rahimahumullah). (Siyar A’laamin Nubalaa13/204 and Tahzeeb-ul-Kamaal 11/356)

Eminent Students:

Just as Allah Ta‘ala had blessed Imaam Abu Dawood with many eminent Ustaads, Allah Ta‘ala also blessed him with students who were among the leading Muhadditheen of their era. Two such students who narrate Hadith from Imaam Abu Dawood (rahimahullah) are Imaam Tirmizi (rahimahullah) and Imaam Nasaai (rahimahullah). (Siyar A’laamin Nubalaa 13/205-207)

Close Relationship with Imaam Ahmed bin Hambal (rahimahullah):

Imaam Zahabi (rahimahullah) has mentioned, “Imaam Abu Dawood (rahimahullah) acquired the knowledge of fiqh from Imaam Ahmed bin Hambal (rahimahullah), and he remained with him for a lengthy period, (benefiting from him).”

Imaam Zahabi (rahimahullah) thereafter mentions that on account of Imaam Abu Dawood (rahimahullah) remaining closely attached to Imaam Ahmed (rahimahullah), he began to resemble him in his conduct and mannerisms, and the conduct and mannerisms of Imaam Ahmed (rahimahullah) was the conduct and mannerisms of the sunnah.

Imaam Zahabi (rahimahullah) says, “Imaam Abu Dawood (rahimahullah) resembled Imaam Ahmed (rahimahullah), just as Imaam Ahmed (rahimahullah) resembled his ustaad, Imaam Wakee (rahimahullah).

“Imaam Wakee (rahimahullah) resembled his ustaad, Imaam Sufyaan (rahimahullah), and Imaam Sufyaan (rahimahullah) resembled his ustaad, Imaam Mansoor (rahimahullah).

“Imaam Mansoor (rahimahullah) resembled his ustaad, Imaam Ebrahim (rahimahullah), who resembled his ustaad, Imaam Alqamah (rahimahullah). Imaam Alqamah (rahimahullah) resembled his ustaad, Hazrat Abdullah bin Mas’ood (radhiyallahu ‘anhu).”

As for Hazrat Abdullah bin Mas’ood (radhiyallahu ‘anhu), then his student, Imaam Alqamah (rahimahullah), mentions that he resembled Rasulullah (sallallahu ‘alaihi wasallam) in his blessed conduct and mannerisms. (Tabaqaat li-Subki 2/296)