{By two and two} (duo duo). This repetition of the numeral
instead of the use of ana duo or kata duo is usually called a
Hebraism. The Hebrew does have this idiom, but it appears in
Aeschylus and Sophocles, in the vernacular _Koin(825f) (Oxyrhynchus
Papyri No. 121), in Byzantine Greek, and in modern Greek
(Deissmann, _Light from the Ancient East_, pp. 122f.). Mark
preserves the vernacular _Koin(825f) better than the other Gospels
and this detail suits his vivid style. The six pairs of apostles
could thus cover Galilee in six different directions. Mark notes
that he "began to send them forth" ((8872)xato autous apostellein).
Aorist tense and present infinitive. This may refer simply to
this particular occasion in Mark's picturesque way. But the
imperfect tense edidou means he kept on giving them all through
the tour, a continuous power (authority) over unclean spirits
singled out by Mark as representing "all manner of diseases and
all manner of sickness" ( Mt 10:1 ), "to cure diseases"
(iasthai,  Lu 9:1 ), healing power. They were to preach and to
heal ( Lu 9:1  Mt 10:7 ). Mark does not mention preaching as a
definite part of the commission to the twelve on this their first
preaching tour, but he does state that they did preach ( 6:12 ).
They were to be missioners or missionaries (apostellein) in
harmony with their office (apostoloi).