This volume presents firstly comparative research in one conceptual domain of ancient Jewish/Christian thought, and secondly, points out that modern critical theology, past and present, has misunderstood ancient Jewish and Christian perfectionism. It examines three unrelated samples of perfectionistic espousal from Second Temple Judaism in a Palestinian setting contemporaneous with the rise of Christianity. The relationship between ethics and eschatology reveal certain basic commonalities and specific individual divergences. Three unrelated samples of perfectionistic espousal are also taken from the New Testament, sharing some of the same basic commonalities with the Jewish writings. They also share some basic commonalities in contradistinction to them. The real basis for Jewish perfectionism was covenantal relationship, involving conforming behaviour expressive of elect relationship. The basis for New Testament perfectionism is relationship to Christ within the gracious provision of the New Covenant. Perfection is a relational dynamic, one that can coexist with and increasingly conquer sin.It is human destiny as relationship with God, presently opened to all who identify with the new work of God accomplished by Jesus.