Jamieson, Fausset and Brown on Romans 16:23

23. Gaius mine host, and--the host

of the whole church--(See Ac 20:4). It would appear that he was one of only two persons whom Paul baptized with his own hand (compare 3Jo 1). His Christian hospitality appears to have been something uncommon.

Erastus the chamberlain--"treasurer."

of the city--doubtless of Corinth. (See Ac 19:22; 2Ti 4:20).

and Quartus a brother--rather, "the" or "our brother"; as Sosthenes and Timothy are called (1Co 1:1; 2Co 1:1, Greek). Nothing more is known of this Quartus.