ISB ~ 2 Corinthians 1 v1

an apostle:A messenger of the gospel commissioned directly by Christ (Acts 26:12-18) and a witness of his Resurrection (1 Cor 9:1). Throughout this letter Paul asserts and defends his apostolic authority against those who have challenged it. He was established in this office by God’s will and call, not by his own recommendation (2 Cor 1:21; 2:17).

Timothy:A faithful companion of Paul (Acts 16:1-3) and a familiar figure to the Corinthians (Acts 18:5; 1 Cor 4:17). See note on 1 Tim 1:2.

the Church of God:The local community in Corinth, which is an integral part of the universal Church. Paul himself is the founder of this congregation (Acts 18:1-11).

Achaia:A Roman province in southern Greece whose capital city was Corinth. Paul is writing just north of Achaia in the province of Macedonia (2:13; 7:5).