Shared ground
Paul opens by identifying himself and grounding his role in God’s initiative: he is “called” as an apostle of Jesus Christ, and this calling is “through the will of God.” That is an explicit claim of authority, but it is framed as received rather than self-made.
Paul also names Sosthenes as “our brother,” presenting him as a trusted Christian associate connected to the message. Even in these first lines, the letter is not merely personal; it is linked to a wider Christian network.
The recipients are described in layered ways. They are the “assembly of God” located in Corinth (they belong to God, yet they are a real local group). They are also “sanctified in Christ Jesus” and “called…saints,” which presents a strong identity claim before any of the letter’s later corrections.
Finally, Paul’s greeting is not just polite. He speaks a blessing of “grace” and “peace,” and he names the shared source as “God our Father and the Lord Jesus Christ.”
Where interpretation differs (only where needed)
Sosthenes’ role: Some read Sosthenes as a co-sender in a strong sense (sharing responsibility for the letter’s content). Others read him as a named coworker whose presence supports Paul’s message, without implying equal authorship. The text clearly associates him with the letter, but it does not spell out how much he contributed.
“Sanctified” and “called…saints”: Some take these phrases mainly as a settled status God gives to the Corinthians “in Christ,” even if their behavior needs serious correction later. Others hear a stronger emphasis on vocation: they are called to live as God’s set-apart people, which the letter will insist they must take seriously. The text itself highlights identity and calling; it does not explicitly explain the balance between status and lived consistency.
“Every place, both theirs and ours”: Some understand this as referring to local meeting places shared by different communities (“their place and ours”). Others take it more broadly: believers everywhere call on Jesus, whether in Corinth or where Paul and his coworkers are. The phrase clearly widens the horizon beyond Corinth, but the precise nuance of “theirs and ours” is debated.
Why the disagreement exists
These lines are compact and relationship-focused. Paul uses phrases (“with all who call…,” “sanctified,” “called”) that carry rich meaning but little immediate explanation. Also, ancient letter openings often name associates without clarifying whether they helped write, delivered the letter, or simply stood with the sender.
What this passage clearly contributes
It establishes (1) Paul’s claimed commission as God-given, (2) the Corinthians’ identity as God’s people “in Christ,” (3) the connectedness of the Corinthian church with all who acknowledge Jesus as Lord, and (4) the shared framework of divine favor and wholeness captured in “grace” and “peace.” It also sets a tone: later critique will be spoken to people Paul already addresses as belonging to God and sharing allegiance to Jesus.