{As he was praying} (en t(9369) einai auton proseuchomenon).
Common Lukan idiom of en with the articular infinitive for a
temporal clause, only here Luke has the periphrastic infinitive
(einai proseuchomenon) as also in  11:1 . This item about
Christ's praying alone in Luke. {Alone} (kata monas). In the
N.T. only here and  Mr 4:10 . Perhaps ch(9372)as (places) is to be
supplied with monas (lonely places). {Were with him} (sun(8873)an
aut(9369)). This seems like a contradiction unless "alone" is to be
taken with sun(8873)an. Westcott and Hort put sun(886e)t(8873)an in the
margin. This would mean that as Jesus was praying alone, the
disciples fell in with him. At any rate he was praying apart from
them.