3 Dear friends, although I was eager to write you about the salvation we share, I found it necessary to write and exhort you to contend for the faith that was delivered to the saints once for all.
The Reformation Study Bible note on “the faith” is helpful (click “show resources” in the upper right).
Here “faith” indicates the content of the message taught by the apostles and held in common by all Christians, rather than the personal exercise of trust by a believer. Christianity includes an authoritative body of belief given by God to the church through the apostles (1 Cor. 15:3–8). Together with the Old Testament (Eph. 2:20), this apostolic witness, as found in the New Testament, is the standard for the church (2 John 9,10).
This faith was delivered to us.
We did not package it.
It wasn’t our idea.
We received it.