While all the synoptic Gospels include a mission of the Twelve, only Luke adds a second mission of the 72 (or in many manuscripts the 70). The numbers are symbolic perhaps of the 72 nations of the world in Genesis 10, or of the 70 elders whom Moses chooses to be assistants (Ex. 24:1). This second Lukan mission prepares the way for the universal mission of the church in Acts and repeats the motif from Isaiah that God’s goodness is inclusive of all peoples.
The Lukan missionaries are to travel light, with a deep trust in God and in those who will receive them. Their first words whenever they enter a house are Peace to this household, and if a person characterized by peace welcomes them, God’s peace will rest on that house. Peace is the biblical shalom, wholeness or security, the result of a right relationship with God and neighbor (see Is. 32:17, Justice will bring about peace; right will produce calm and security). The God of Isaiah promises the returning exiles, I will spread peace over Jerusalem like a river (NAB translates, prosperity over, but the original Hebrew is shalom). In Isaiah God who brings peace is compared to a mother cradling and comforting a child (also Is. 45:15).
Yet another voice hovers behind Isaiah’s vision of peace and the Gospel message. Jesus foretells rejection of the traveling missionaries and demonic opposition, and through the centuries Isaiah’s Jerusalem has most often been a mother mourning for her children. (As I write these lines two car bombs have just gone off there.) Complete peace with God and within the human family may never unfold in human history, but it remains both a mandate and an ideal for which Christians in mission will continue to suffer. In urging dialogue to break down those religious barriers that have fostered wars of religion, Pope John Paul II wrote: The name of the one God must become increasingly what it is: a name of peace and a summons to peace (At the Beginning of the Third Millennium, No. 55). Wherever they travel Christians must first say, Peace to this household.