{For a testimony unto them} (eis marturion autois). Not in
Matthew.  Lu 9:5  has "for a testimony against them" (eis
marturion epi autous). The dative autois in Mark is the dative
of disadvantage and really carries the same idea as epi in
Luke. The dramatic figure of {shaking out} (ektinaxate,
effective aorist imperative, Mark and Matthew), {shaking off}
(apotinassete, present imperative, Luke).