Wholeness is the inmost principle of the Sermon on the Mount.
Gerhard Lohfink understands the Sermon on the Mount (Matt 5-7) against the background of the covenant relationship between YHWH and the people of Israel described in the Old Testament. According to Lohfink this covenant is about wholeness: “God has turned wholly and undividedly towards this people, and correspondingly Israel is to live whole and undivided before its God.” This wholehearted faithfulness toward YHWH is perhaps most clearly articulated in Shema. “Hear, O Israel: The LORD is our God, the LORD alone. You shall love the LORD your God with all your heart, and with all your soul, and with all your might” (Deut 6:4-5). Birger Gerhardsson has argued in different studies for the importance of Shema for the New Testament. Lohfink's emphasis is somewhat similar to Gerhardsson's. This wholeness could be expressed in different ways using a set of different words such as holy, righteous, blameless and perfect.
In one central verse in the Sermon on the Mount one of these words is used: “Be perfect, therefore, as your heavenly Father is perfect” (Matt 5:48). This verse seems to be some sort of header for the so-called antithesis (Matt 5:21-48) and as such summarize these examples of true faithfulness to the Torah as interpreted by and fulfilled in Jesus (Matt 5:17-20). Being faithful, then, is about being “perfect” (teleios). If Lohfink is right, then the perfection in question is not “the Greek ideal of perfection,” that is, “an autarchic personality at the pinnacle of life, possessing all the virtues and so mature in all of them that increase is impossible.” Instead, perfection is about undivided loyality in a relationship. It is about wholeness. If so, then Matt 5:48 could be paraphrased “Be whole and undivided in your loyalty [to God], therefore, as your heavenly Father is whole and undivided [towards his people and humanity].” It seems to be assumed that a “genuine attainment” of this wholeness is possible (see e.g. Matt 5:16; 7:12, 24-26; 28:20) although not necessarily a “total attainment” given that the kingdom of heaven/God is not fully realized.
In fact, Lohfink suggests that wholeness is the “inmost principle” of the Sermon on the Mount. Wholeness is not only the background against which to understand Matt 5:48, but also a sort of hermeneutical key to or the main theme of the whole Sermon. But could Matt 5:48 and the Sermon as a whole really be understood in this way? That will be the question for a second and a third blog on the Sermon of the Mount.
This is part one of a series of blogs on the Sermon on the Mount.
 For what follows, see Gerhard Lohfink, Does God Need the Church? Toward a Theology of the People of God (Collegeville: Liturgical Press, 1999), 271-277. See also idem., Wem gilt die Bergpredigt? Beiträge zu einer christlichen Ethik (Freiburg im Breisgau: Herder, 1988), 65-98.
 Lohfink, Does God Need the Church?, 273.
 Ibid., 275.
 Christopher D. Marshall, Beyond Retribution: A New Testament Vision for Justice, Crime, and Punishment (Studies in Peace and Scripture; Grand Rapids; Auckland: Eerdmans; Lime Grove House, 2001), 18.
 Lohfink, Does God Need the Church?, 275.