From NT Wright Online: Learning from Paul Together

One would not know, from many Pauline interpreters, that the unity of the church was one of Paul’s overriding passions. The famous doctrine of justification, used in the sixteenth century and later as a means of dividing the church, was itself actually designed to affirm the unity of all believers across lines of ethnic and other divisions. That is clear particularly from its first exposition in Galatians 2, where Paul confronts Peter because Peter has given in to pressure from hard-line Jewish Christians and has separated himself from table-fellowship with Gentile Christians. Paul’s response, in a brief articulation of justification, is that all who share Messiah-faith belong at the same table. All alike have died with the Messiah and have come through to new life in him, and that new shared life is the one and only source and marker of their identity.