QUARTUS (kwôr'tŭs, Gr. Kouartos). A Christian man of Corinth whose greetings Paul sent to the church at Rome together with those of Gaius and Erastus (Rom.16.23). No doubt he was a friend and assistant of Paul and a worker in the Corinthian church. There is an old tradition that he was originally one of the seventy disciples or missionaries Jesus sent out in Palestine (Luke.10.1).
QUARTUS kwor’ təs (Gr. Κούαρτος, G3181), a man mentioned in Romans 16:23 as an associate of Paul, who wished to send a greeting to the Christians in Rome. The name is Lat. and appears in its Gr. form in the non-canonical subscription to the TR VS of 1 Corinthians. No other mention in the Scripture, nor any other in the patristic annals has been attested.
International Standard Bible Encyclopedia (1915)
A Christian in Corinth who with "Erastus the treasurer of the city" sent greetings to the Christian community in Rome (Ro 16:23). He is known to Paul only as a Christian, "the brother."