{Messiah cometh} (Messias erchetai). Hebrew word in N.T.
only here and  1:41  and explained by Christos in both places.
The Samaritans looked for a Messiah, a prophet like Moses ( De
18:18 ). Simon Magus gave himself out in Samaria as some great
one and had a large following ( Ac 8:9 ). Pilate quelled an
uprising in Samaria over a fanatical Messianic claimant
(Josephus, _Ant_. XVIII. iv. 1). {When he is come} (hotan elth(8869)
ekeinos). "Whenever that one comes." Indefinite temporal clause
with hotan (hote, an) and the second aorist active
subjunctive. Wistfully she turns to this dim hope as a bare
possibility about this strange "prophet." {He will declare unto
us all things} (anaggelei h(886d)in hapanta). Future active
indicative of anaggell(935c), old and common verb to announce fully
(ana, up and down). See also  16:13 . Perhaps here is light on
the knowledge of her life by Jesus as well as about the way to
worship God.