In Paul's letter to the Phillipans, typically dated 50-60 AD, Paul says:
Your attitude should be the same as Christ
You being the very nature(Form) of God, did not consider equality to God as something to be held on to (grasped), but made himself nothing, thaking the very nature of a servant being made in human likeness
And being found in appearance as a man he humbled himself and became obident to death, even death on the cross
Therefore God exalted him to the highest place and gave him a name thatis above all names that at the name of Jesus every knee shoudl bow in heaven and earth and under the earth and every tounge confess that Jesus Christ is Lord to the glory of God the Father.