Luke 10 records similar instructions given to the seventy when they are sent out, although that is a different occasion. Although some of the sayings in this discourse were also spoken at other times, on the basis of Matthew 11:1 we can be sure that what we find in this chapter is not just Matthew’s collection of all that Christ said on the subject of mission, but were all spoken to them on this occasion.
The disciples are sent out in pairs for companionship; they are to encourage each other and their common faith is to strengthen each other, so it won't be one messenger in each village or town; it will be a pair, and they’ll work together. They’ll work together for a measure of companionship and support. It is for the sake of witness, according to the ancient God-given principle: ‘at the mouth of two witnesses, or at the mouth of three witnesses, shall the matter be established’ (Deuteronomy 19:15). It is for the sake of prayer: ‘For where two or three are gathered together in my name, there am I in the midst of them’ (Matthew 18:20). So in their witness today, the churches follow the same pattern and where possible send their witnesses out two by two (Revelation 11:3).