Some scholars think that Sabin was omitted from the Namelist of Bulgarian Rulers because he was a Slav, but his name could indicate Latin or even Iranian origins.
Sabin rose to the throne after the murder of Telets in 765 and represented that part of the Bulgarian nobility which was seeking a policy of accommodation with the Byzantine Empire.
Accordingly, he swiftly dispatched secret emissaries to Emperor Constantine V Kopronymos, who had recently defeated Sabin's predecessor Telets, seeking to re-establish peace.
When the negotiations were discovered, the Bulgarians rebelled and held an assembly, in which they accused Sabin of causing Bulgaria's enslavement by the Byzantines.
In 768 Sabin attended Constantine V's negotiations with a new Bulgarian ruler, Pagan, but the emperor's words on behalf of the former monarch made little impression.