I have been persuaded for some time that Galatians was Paul’s earliest letter, written approximately AD 49-50. This is significant because, according to some conservative scholars, Galatians 1:1-5 contains the earliest written interpretation of the death of Jesus in the New Testament.
The four Gospels were written after Galatians, as were the other letters (with the exception of James), Acts, and Revelation. So although Acts reports some early church history after the ascension of Jesus and before Paul was every converted, the book was still written after Galatians.
Put another way, Galatians 1:1-5 was the earliest New Testament record of what leaders–Paul in particular–were teaching about the cross (the letter of James does not provide any explicit teaching about Jesus’ death).
“Paul, an apostle–not from men nor through man, but through Jesus Christ and God the Father, who raised him from the dead….Grace to you and peace from God our Father and the Lord Jesus Christ, who gave himself for our sins to deliver us from the present evil age, according to the will of our God and Father” (Gal 1:1, 3-4).
Four observations can be made. According to the earliest New Testament record of the interpretation of the cross,
(1) Jesus’ death was voluntary (“gave himself”)
(2) Jesus’ death was substitutionary (“for our sins”)
(3) Jesus’ death was planned (“according to the will of our God”)
(4) Jesus’ death was vindicated (“who raised him from the dead”)
The earliest New Testament testimony about the cross is worth our reflection. In summary, the early church taught, proclaimed, and wrote about a risen Lord who had freely borne our sins on the cross in fulfillment of his Father’s plan.